A top five, ehhh?
Gungrave sits on this list before even contemplating.
Bleach has lost some of it's luster in recent days, but the new filler arc looks promising, still not on my list.
One Piece got a little slow at some times, but has always entertained me through it's (current) 412 episodes.
Spice and Wolf is making a comeback with a second season, First season based primarily on 1800 European mercantile, second season based on (so far) the differences between a traveling merchant and a storefront merchant.
Hellsing (Ultimate OVA of course) With bodies shamelessly ripped apart, characters as dark and their shadow in an overcast midnight forest, a the return of Das Drittes Reich, and London, England covered in enough blood to fill an army of millions I think many can enjoy.
And for my fifth, I am just going to list a number of Movies/specials/single animations:
Voices of a Distant Star
Toki wo Kakeru Shoujo(The girl who leapt through time
The place promised in our early days
Princess Mononoke
Paprika
Kiki's Delivery service