Well, Third Impact was meant to happen over the past couple of days and it didn't, so all of Neon Genesis Evangelion's endings were disappointing (and weird). But seriously, in a poetic sense, I liked Baccano!'s sense of a never-ending story that would continue after the ending.
I've always liked Hetalia's endings. I also like what I've heard of the Japanese One Piece ending songs.
I can't decide between... FMAB with dramatic walking and epic hand holding [YOUTUBE]0svawsrPfOg[/YOUTUBE] Free eternal Sumer with astronauts, hot cops and MI6 [YOUTUBE]fi35L4dZ5Ic[/YOUTUBE]