If it's on your desk you can probably lavish a bit more attention on it as you'll presumably be sitting at it at work. A bonsai tree would look great and would appreciate a little attention. The key to a successful tree is to choose one not on what looks good in homebase, but to do a quick search online and try to match the species to your desk environment. Are you by a south facing window or is it very shady?
Edit: Venus flytraps are cool, but I've always found them to be a bit tricky. I suppose if you keep it well watered you'd be fine, but it would need watering if you went away for more than a few days.