Whatever you like... But, don't get something to get one... Get something that had meaning... I happen to love tattoos, my dad does too, all his tattoos have a story and or reasoning to why he got it... It's better that way
Something that will just as good and cool 30 years from now as you think it will today! Remember it can also effect future employment, and how people perceive you! At 16 my son thought it would be cool to have a squirrel with his claws reaching up done on his inner thigh! Didn't get it done, now at 24 he doesn't think that would have been so cool!
Right now I would go with none, because if you are serious about getting one, then coming on a site like this and asking for ideas is really a bad idea, even if people supposedly give you a good idea or an idea that they think is good. There have been many occasions I have thought about getting a tattoo myself, and once I was so close, I actually put a down payment on one, but missed the appointment due to intoxication, and did not get my down payment back. (The dude did me a favor, I am currently proud that I'm without ink, still, every once in a while, I harbor a thought of getting one, but money, and laziness, and ADD prevent me from taking any further action.)