I'm not going to be sarcastic or rude, because that is not behavior tolerated in these forums. If you didn't know the question, at least you were brave enough to ask. Farfolen just about covered the topic though. Cases can be quite fun if you look beyond their mere "purpose" and look at it as an art form (for geeks anyways). You can add all sorts of mods to it like windows, lights, colored fans, etc. I personally was too lazy to mod a case myself, so I got one of those aluminum Antec type full tower cases with a window in the side (kind of looks like the Alienware cases). It is a striking blue and is a pleasure to work with. When looking for a case, I would suggest you take into account looks, room inside, placements for fans, rounded edges (cutting yourself kind of hurts), room for expansion, and a standard form factor (ATX, all variants). If you have any other questions, just ask, we don't bite (most of use anyways).
"God created man. Samuel Colt made them equal."
"Government does not tax to get the money it needs; government finds a need for the money it gets." - Ronald Reagan