Baccano!
karas
Hellsing
Bleach (yeah, i said it)
Gun Slinger Girl
probably my top 5 atm. Odd thing about bleach for anyone put off by its filler arcs. It does a better job at making the fillers less redundant than most animes. Naruto has its moments and if you got into D-GreyMan (also good) you'd see that bleach has no where near the completely off the wall filler episodes. I find bleach to be well done.
If you haven't seen them Karas, Baccano! and Gunslinger Girl are all a must to watch. Karas is only 6 episodes and GG and Baccano! are only 13. Definately worth the day it takes to BT them. Each serious is entirely unique in its own right and very enjoyable.