As an addition to the question, Charlemagne’s sword is famously known as Joyous. Was it actually called that by Charlemagne or is that later legend?

I suspect you meant Europe, but I know New Zealand, so that's where I'll answer for. Also note my te reo is appalling, so translations will only be given when they're in the source, or really obvious, and macrons will be a little inconsistent given the different spelling conventions in the different sources.

There were a large amount of named weapons in Māori culture, which is not terribly surprising. The weapons of important and successful people would amass considerable mana of their own. Mana is rather a big topic and kind of peripheral to this discussion, but can be thought of as equivalent to prestige, or spiritual power. It was proven via success and came from a number of sources, such as descent (for the mana of people), or association with people of rank. The greater a person or object's mana, the more sacred or forbidden they became. The Māori world was highly personified, and, in any case, many weapons were decorated in fairly anthropomorphic ways: long clubs usually with a Janus face on the shaft, making the point a tongue and the blade a body, and short clubs of wood or whalebone with butts in the form of a head, or a figure on the back. It became therefore very natural to consider important weapons as having some level of personality of their own.

An couple of examples of weapons from traditional history would be the weapons of Te o Tane. Te o Tane lived near Wairoa, likely around the 17th century. He was renowned for his size, and when on campaign his brother-in-law Taiwhakahuka would be required simply to carry his weapons: a patu (or 'club' example) named Te Ate-o-Hine-pehinga (the liver of Hine-pehinga: his grandmother) and a taiaha (example) named Te Atero-o-Te-Arawhiti out of respect for his mother (Te Arawhiti).

In more recent times, Herea, later known as Te Heuheu Tukino (d. about 1820) used a pouwhenua (example) called Arerokapakapa (quivering or fluttering tongue. The point of a taiaha or pouwhenua is called the tongue).

Some of the most interesting and highly respected weapons were mere pounamu (or simply patu pounamu in the South Island). Pounamu, or jade was the hardest, and one of the sharpest after obsidian, materials known to Māori before iron was introduced. It was only found in the more sparsely populated South Island, so was often passed long distances, and enormous amounts of time were spent on making tools or weapons out of it. Mere pounamu were often given as gifts at peace-makings or other very important events. One such weapon is Tuhiwai a weapon that was given to the Ngāti Toa chief Te Rauparaha (one of the best-known figures of the Musket Wars) by the South Island tribe of Ngāi Tahu to make peace. It was later given to Te Rangihaeata, Te Rauparaha's nephew (painted here holding it), who probably used it to execute the New Zealand Company officials and surveyors after the Wairau affair. 'Tuhiwai', which means to strike the water, is a reference to the way Te Rauparaha used the mere in divination. It shares the name with a mere (on left), now in the British Museum, that was owned by Te Hiko-o-te-rangi (also of Ngāti Toa), and was presented to Governor Grey (it was considerably fire-damaged when Government House burnt down, which explains the cracks and discolouration).

Another, unusually large, mere connected with Ngāti Toa is Tawhito whenua (whenua is 'land'). It was owned by Te Kēkerengū of Ngāti Ira. At some time in the 1820s he was captured, along with his mother Tamairangi (a woman of very considerable mana who was carried any time she needed to travel) by an alliance including Ngāti Toa. Before being executed Tamairangi asked for permission to sing a farewell song to her lands. She performed it so movingly that Te Rangihaeata (who was among their captors) spared their lives and took them to the Ngāti Toa stronghold of Kapiti Island. However he took Tawhito Whenua from them (this situation lasted until Te Kekerengu slept with one of Te Rangihaeata's wives, and they decided it might be a good time to move elsewhere. Love is blind and all that, but it probably wasn't the best decision ever).

It was considered an honour to be killed by a greenstone weapon, and defeated people of high birth would often request it. During the siege of Puke-kararo a fort (pa) on the Mahia Penninsula (in about the 1820s) a man named Kauhu tried to escape with a child of high rank on his back (some traditions say Te Kani-a-Takirau, Mitchell believes that the dates line up wrong, and it must have been Hirini Te Kani). He was caught by one of the besieging chiefs, Potiki from the Hauraki area, and about to be killed with his iron hatchet, when he presented Potiki with a mere called Te Heketua and asked to be killed with it rather than a common weapon. Potiki took the weapon, gave Kauhu his hatchet, and let him go free with the child. A song referencing Te Heketua can be found here. Smith is a rather dodgy source for a number of reasons, but it is definitely a 19th century song referencing the weapon I suppose, even if it's not actually early 19th century.

There doesn't seem to be an overall theme to the naming. Some have very warlike meanings, such as Arerokapakapa or a stone club (patu onewa) in Auckland Museum (which I can't find a picture of) named Kaitangata or 'man eater', but others are named for more obscure reasons or are just odd (I presume Te Heketua was named for something other than the literal meaning).

A lot of my sources were actually museum websites and the dictionary of New Zealand biography (also online), but I also used 'Takitumu' by J. H. Mitchell (Tiaki Hikawera Mitira), which is pretty old and rather romanticised, but quite interesting.