It looks to be cuneiform. It's one of the earliest forms of writing, developed in ~ 4th millennium BCE in what's now Iraq. However, you will be very lucky to find someone who can translate it; I remember reading a comment in an article than only 150-200 people worldwide can read cuneiform these days. (There was apparently some discussion over whether we could program computers to be able to read cuneiform, but unfortunately I don't know what, if anything, came of it.) Museums are sitting on mountains of the stuff, and we've got no clue what's in most of it because so few people can translate, and of course, it didn't stay exactly the same from region to region and era to era, much like any other writing system.
Cuneiform is generally easy to recognize because the marks are so distinctive. It wasn't made to be written as such; scribes had a stiff reed "pen," typically with a wedge at one end (see how each line is larger at one end than the other?), that they used to make marks and depressions in soft clay. The clay tablets could either be softened and reused as desired, or fired in a kiln in order to preserve the writing permanently and prevent unauthorized changes. However, that did come at the cost of making it far more breakable.
Ea-nasir, Comcast of the ancient world: In later periods, scribes were sufficiently accessible to the general public that writing wasn't solely used by the elite. One of the most famous cuneiform records, and one that's made the rounds even on non-history related sites, is from 1750 BC, and it's basically a complaint letter from a copper merchant named Nanni to a fellow merchant and smelter, Ea-nasir:
When you came, you said to me as follows: “I will give Gimil-Sin (when he comes) fine quality copper ingots.” You left then but you did not do what you promised me. You put ingots which were not good before my messenger (Sit-Sin) and said: “If you want to take them, take them; if you do not want to take them, go away!”
What do you take me for, that you treat somebody like me with such contempt? I have sent as messengers gentlemen like ourselves to collect the bag with my money (deposited with you) but you have treated me with contempt by sending them back to me empty-handed several times, and that through enemy territory. Is there anyone among the merchants who trade with Telmun who has treated me in this way? You alone treat my messenger with contempt! On account of that one (trifling) mina of silver which I owe you, you feel free to speak in such a way, while I have given to the palace on your behalf 1,080 pounds of copper, and Umi-abum has likewise given 1,080 pounds of copper, apart from what we both have had written on a sealed tablet to be kept in the temple of Samas.
And so on. Press 0 into your clay tablet to speak to a customer service representative. Your tablet is very important to us ...
Unfortunately, that's as much as I can do because this isn't my field, but if you're interested in seeing more translated records and correspondence, there's a PDF copy of A. Leo Oppenheim's Ancient Mesopotamia: Portrait of a Dead Civilization available here. This has been on my to-read list for a while.
If /u/Cenodoxus is right (and I'm willing to bet there are more people around who can read cuneiform than that!) you're in luck that Reddit is a den of geeks! As he points out, the script is cuneiform - specifically, it looks to be Neo-Assyrian or Neo-Babylonian cuneiform (but more probably the former) Old Babylonian (thanks, /u/Sandorra).
The value of the individual characters, in order, is GIŠ - GÍN - MAŠ. You'd never pronounce it that way, though: this is how you write the name Gilgamesh! Usually, it would have the DINGIR sign in front of it, so I'm curious where you found it.
Source: Any sign list - I use Rykle Borger's (the basic one in Babylonisch-Assyrische Lesestücke, Rome: Pontificium Institutum Biblicum, 2006 suffices for most basic texts).
May I ask where you found this? It's not every day that someone comes up with a bit of cuneiform. Is it just random, is it from a movie?
