MULTIPLE GENRE
Bakemonogatari - My personal favorite anime ever. Dialogue driven and it's from Studio SHAFT
Katanagatari - As mentioned before, very well done.
Baccano! - Story with multiple main characters with the same story being told from different points of view.
Durarara! - From the creators of Baccano!
ECCHI
Hyakka Ryouran Samurai Girls - The title gives it away kind of >.>... loved the animation of this
High School Of The Dead - Ecchi zombie slaughtering. Gotta love it
Any harem series (To-LOVE-ru, Love Hina, Infinite Stratos etc) google "harem anime" and you'll get your fix
COMEDY
Seitokai Yakuindomo - verbally perverted, girls are the pervs. Hilarious with every meaning of the word.
Seitokai no Ichizon - Comparable to ^, but other characters and personalities.
Working!! - About a family restaurant with the most original character traits you can find. Second season has been announced! (for quite a while though)
Great teacher Onizuka - A classic about a ex-gang leader becoming a school teacher.
ROMANCE
CLANNAD (After Story) - I'd recommend this to anyone, just make sure to watch all the way through the end.
Kanon^ this really
As for the rest, (mecha action and stuff) after watching all of Naruto, One Piece, Bleach, Hitman Reborn etc I needed to take a break from the "Ima going super saiyan to protect my friends GWHAAAAAAAAAH" shounen style series.
I've seen many people recommend Soul Eater, my advise, don't. or at least watch until episode 35 and start reading the manga from then on, as that where the fillers start and I'll tell you now, the anime ending is the LAMEST ending in the history of mankind.
