1) Baccano! - Seriously, I never thought I'd like an anime as much as this. When I started watching anime in general, I did it to kill time. After I watched this show, I realized that anime could indeed be really, really, really good.
2) The Melancholy of Hahuri Suzumiya - There is a kind of unhinged, uncanny genius to this show. It was just so brilliant, and all from a concept that could easily have degraded into cliche and overpowering stupidity (see: the second season). The only fault I found is that there isn't enough of it.
3) Full Metal Alchemist Brotherhood - Right now, this is the only anime I allow myself to watch, with finals and term-end projects looming. I come home very Sunday night and rush to watch the latest episode. This is truly a show that has something for everyone.
4) Black Lagoon - Somehow, this show balances an insane amount of kinetic energy with just enough character development to make the viewer care about what the results of the gunfights and explosions will be. And unlike Hahuri, the second season is just as good as the first.
And that's it. I've watched plenty of other animes, but no other have really stuck out enough to make it to my 'Top 5' list. Maybe that'll change in the future?