It depends on what sort of battle you're looking for, and how big your project is. It's possible to write a book about some of the accounts in Xenophon. Some of the ones you could consider:

• Battle of Koroneia, 394 BC (source - Agesilaos 2.6-16). This battle is not very remarkable except for the details of its description; it offers some of the few and often cited details of close combat among Greek hoplites and the mess it left behind.

• Battle of the Nemea, 394 BC (source - Hellenika 4.2). This is the largest pitched battle ever fought between Greek city-states (unless we follow high estimates for the armies at Second Mantineia). Possibly as many as 50,000 hoplites faced each other at the Nemea. I also did a podcast on this battle.

• Battle of Lechaion, 390 BC (source - Hellenika 4.5.11-17). This is the story of how a Spartan army unit was destroyed by Iphikrates and his light infantry. Some of my other podcast revolved around this.

There are many other ones in Xenophon, and many others in other Greek sources. Let me know if any of these fit the bill.

Obviously there are countless possibilities for this but one really interesting and graphic first-hand account of battle I can think of is Bernal Diaz's account of the Battle of Tenochtitlan in 1520 in which he with around 1,000 Spanish conquistadores and a few thousand native allies (Tlascalans) under Hernan Cortez were besieged by tens of thousands of Aztec warriors inside the palace in the city of Tenochtitlan. The city was located on an island in the middle of Lake Texcoco and the Spanish weren't able to escape from the city because the Aztecs had destroyed the causeways leading off the island in order to trap them inside. What followed was a week of extremely bloody close quarters street fighting as the Spaniards tried to battle their way out. It ended with a final desperate attempt by the Spanish to escape from the city at night via a makeshift causeway during which over half of the Spanish were killed or drowned. Bernal Diaz was an eyewitness and his full account is in his book The Conquest of New Spain but I can quote some excerpts:

I will describe the whole of the battle. We were struck by the tenacity of their fighting, which was beyond description. Neither cannon, muskets, nor crossbows were of any avail, nor hand-to-hand combat, nor the slaughter of thirty or forty of them every time we charged. They still fought on bravely and with more vigour them before. If at times we were gaining a little ground or clearing part of a street, they would pretend to make a retreat, in order to lure us into following them. By attacking thus at less risk, they believed they would prevent us from struggling back alive, for they did us most damage when we were retiring.

… I do not know why I am writing so calmly, for some three or four soldiers of our company who had served in Italy swore to God many times that they had never seen such fierce fighting, not even in Christian wars, or against the French king's artillery, or the Great Turk; nor had they ever seen men so courageous as those Indians at charging with closed ranks.

With great difficulty we withdrew to our quarters, hard pressed by many bands of yelling and whistling warriors, …

Ten or twelve more soldiers were killed that day, and we all returned badly wounded. We spent the night coming to the decision that in two days' time every able-bodied soldier in the camp would sally fourth under the protection four engines, which we would construct. …

After settling on this plan, we spent the next day building the machines and strengthening the many breaches they had made in the walls. … I cannot describe the bands of warriors who came to attack us in our quarters, not just at ten or twelve points but at more than twenty. … Not one of us, they shouted, would remain alive that day. They would sacrifice our hearts and blood to their gods, and with our legs and arms they would have enough to glut themselves at their feasts. ... At night too, they went on yelling and whistling in the same way, and discharging showers of darts, stones, and arrows.

When dawn broke we commended ourselves to God and sallied forth with our towers. …

… our horses … were useless to us. For though they charged the enemy bands, they received so many arrows, darts, and stones that, well-armoured though they were, they could not break the enemy's ranks. If they caught up with any Mexicans, these warriors would quickly jump for safety into the canals or the lake, beside which they had raised fresh walls against the horsemen. There many other Indians were stationed with very long lances to finish them off. If our horses were useless, it was equally useless to turn aside and demolish a house, For, as I have said, they all stood in the water with drawbridges between them. To swim across the gap was very dangerous, for they had so many rocks and stones on their fortified flat roofs that it meant certain destruction to attempt it. ... It was no good our risking our lives in this direction, therefore, so we made for the great cue.

… For a long time we could not ascend the cue, although we persistently pressed home our attacks. We did not take the towers, for they were already destroyed, but in the end we reached the top.

… The battle was fierce and the fighting intense. It was a memorable sight to see us all streaming with blood and covered with wounds; and some of us were slain. … we resolved, with much toil and risk of our lives, to return to our quarters. Our towers had been destroyed, all of us were wounded, we had lost sixteen men, and the Indians constantly pressed on our flanks and rear. …

…

We spent the night dressing the wounded and burying the dead, preparing for going out to fight the next day, strengthening and adding parapets to the walls they had pulled down and the breaches they had made, …

…

In view of this situation, Cortes decided that the great Montezuma must speak to them from the roof and tell them that the attacks must cease, since we wished to leave the city. …

… [Montezuma tries to give a speech to the Aztecs but is hit with stones and killed] …

… they came on again with greater force and fury, crying: 'Now you shall indeed pay for the death of our king and lord, and for your insults to our gods. As for the peace you ask for, come out here and we will settle the terms!'

...

In face of all this, Cortes and the rest of us agreed that we would all come out of our camp next day and attack in another direction, … But though we all fought bravely next day and killed many of the enemy, … it was all to no purpose because of the heavy casualties we suffered. …

…

Now we saw our forces diminishing every day, and the Mexicans increasing in numbers. Many of our men had died, and all the rest were wounded. Though we fought most valiantly, we could not drive back the many bands which attacked us by night and day, or force them to a standstill. We became short of powder, and then of food and water. We had sent to ask them for a truce, but because of Montezuma's' death they would not leave us in peace. In fact we stared death in the face, and the bridges had been raised. It was therefore decided by Cortes and all of us captains and soldiers that we should depart during the night, choosing the moment when their warriors were most careless. …

...

An order was now given that a bridge should be made of very strong beams and planks. This we were to carry with us and use in the places where the bridges had been broken. … By the time these dispositions had been made it was already night, and the gold could be divided among those who were to carry it.

...

As soon as we knew Cortes' plan that we should escape during the night, we prepared to move towards the bridges. … The bridge was quickly put in place, and Cortes crossed over with those of the leading detachment and many of the horses. While this was happening the shouts and cries and whistles of the Mexicans rang out, and they called in their language to the people of Tlatelolco … Then all of a sudden we saw many bands of warriors descending on us, and the whole lake so thick with canoes that we could not defend ourselves, since many of our men had already crossed the bridge. While we were in this position, a great crowd of Mexicans charged down on us to remove the bridge and kill and wound our men, who could not help one another. And since misfortune is cruel at such times, one disaster followed another. Because of the rain two of the horses slipped and fell in the lake. Just as we saw this, I and some others of Cortes' detachment struggled to the other side of the bridge, but we were borne down on by so many warriors that, hard though we fought, no further use could be made of it. The channel, or water-gap, was soon filled with the dead horses, Indians of both sexes, servants, bundles, and boxes.

Fearing that we should inevitably be killed, we pushed ahead along the causeway, … There was nothing we could do. ...

Had it been daytime things would have been even worse. Those of us who escaped only did so by the grace of God. … Pedro de Alvarado soon met them, badly wounded, on foot and with a spear in his hand, since they had killed his sorrel mare. With him he brought four soldiers as badly wounded as himself and eight Tlascalans, all of them pouring blood from many wounds.

… When Cortes and the other captains … saw that no more soldiers were coming down the causeway, tears sprang to their eyes. Pedro de Alvarado told them that Juan Velazquez de Leon lay dead at the bridge, with many other gentleman both of Narvaez' company and our own … He said that he and the four soldiers had crossed the bridge in great peril after their horses had been killed, treading on the dead men, horses, and boxes with which the approach to it was choked. …

… we decided to leave the place as quickly as possible, and five Tlascalans, who found a path to Tlascala without following the road, guided us with great precautions until we reached some small houses built on a hill, and beside them a fortress-like cue that was their shrine. Here we halted.

During our retreat we were followed by the Mexicans, who hurled arrows and darts at us, and stones from their slings. The way they surrounded us and continually attacked us was most terrifying. …

… We took refuge in that fortified cue and attended to our wounded … but there was not so much as a morsel to eat. ...

Let me now say that it was pitiable to see our wounds dressed and bandaged with cotton cloths, for being both chilled and swollen they were very painful. But more deplorable was the loss of the gentlemen and brave soldiers who were missing, … I mention these few only, since it would be a long business to write down the names of our many missing comrades. Of Narvaez' company, the majority fell at the bridge, weighed down with gold. ...

Do you have any particular time periods in mind?

The Heights of Courage is a really good book by a tank commander in the Golan Heights during the Yom Kippur War.