woot for liking things for reasons~
Earth Maiden Arjuna - Arjuna is everything. Not only my favorite, but probably the best anime ever. If you ever want to hear what I have to say, go watch this show.
ef ~a tale of memories~ - Everything I wanted. There are shows on my list that I call 'perfect' and those that have spiritual importance to me, and this one borrows a bit of both worlds. Took my favorite staff and pushed them to the max, took my favorite concept and pushed it to the max and virtually reinvented a genre. It's the show that made me become a director and the show that blew me away more than anything I'd ever seen. Ultimately, it might just be the culmination of too many of my personal preferences.
Eureka Seven - The ultimate coming of age tale in my opinion. Entertaining from start to finish and one of the few shows to really get everything done in terms of character and plot development. It was well thought-out and well executed with an unforgettable couple of main characters. It may not be the king of it's craft, but like ef, it appeals to me in a number of ways.
Tengen Toppa Gurren-Lagann - Style. Mad pimp style. Everything.
Martian Successor Nadesico - 'You Get to Burning' really summarizes it all well. It's the soul of a dreamer in the right context. It's a show that really stands up to it's belief in being itself. For the size of it's cast, all the characters are amazing. One of the series I'd consider 'perfect'.