When presented w/ an open ended question like this, rather than demanding more info, I would opt to answer from a personal standpoint. Let the poster figure out what applies to himself. In other words, what woud I look for in a case.
Peronally I have no use for windows, lights, or any bling bling. A case is to hold you componants and to protect them from the environment. If you think a plain case looks ugly, just tuck it under your desk away from prying eyes. Choose function over form.
Should be solid to the point that it doesn't have any rattling or generate any more noise than the case fans. Beyond that, as long as it's sturdy enough to hold the weight of a few drives, a mother board, and a power supply is all you need. And that's not a lot of weight.
Metal edges inside the cases should be smooth and not sharp... although this isn't a deal breaker. If you are careful, you can use a less expensive case without bodily injury... but you HAVE to be careful.
Good air flow. Luckily, CPUs are running a bit cooler these days, but we still want enough fans in the right places to get cool air in and hot air out. Side vents over your CPU and graphics cards are nice.
Air filters are good too... air flow will eventually dump lots of dust on your precious electronics. Filters can help reduce that.
Easy access to the insides. Preverably without any screws, but if it has screws, preferably thumb screws. You don't want to go hunting for the screwdriver each time you need to add or remove a memory stick or replace a defective fan.
Easily replaceable side panels. It's frustrating as hell getting all the little tabs and slots lined up just right and still not ever being sure that the case is closed up right. The seems and gaps should all be tight and uniform. Hopefully there is a nice positive "click" when you pop the panels back on. Should not have to BANG anything in place.
NO DOORS. Who was the idiot who decided that there shoud be a doors on the front of your computer? The only purpose of a door is to add one more step between you and your CD/DVD drive, and to make it that more dificult to fit into a tight space (i.e. need space to swing the stupid door open). It's perfectly useless.
Easy access to USB/FireWire/Mic/Phone jacks. (read: should have USB/FireWire/Mic/Phone jacks) I like the Centurion V which puts them on the top. I believe the new Antach does that too, although maybe set back a bit further than I would like. (Didn't really get a good look at it, so don't quote me.) This way you can park the case under the desk and still have access to these ports without crawling on the floor. If you plan on putting the case ontop of the desk, then probably DON'T want these ports on the top.
Also consider a small form factor (if you use a microATX motherboard). There are those "cubes" (like the X-Qpac) or the flat "home theater" style (looks sort of like a throwback to the old desktop design). Towers are NOT the only choice.
BTW: I like the CoolerMasters. They're not the sturdiest, but the entire front is made of a metal material w/ thousands of holes. It looks nice and allows lots of air. They make the Centrurion which I mentioned.