My most fave in both categories is Ouran High School Host Club. 8D

Other faves:

Manga only:
~Tokyo Mew Mew (HATE the 4Bakas version, "Mew Mew Power," & have not seen the original Japanese version yet)
~Our Kingdom (a yaoi - I don't think they've made it into an anime)
~Alice 19th (Have they made it an anime yet? o0; )
~Absolute Boyfriend
~Midori Days (I haven't watched the anime yet.. >>;; )
~Pretear (afraid to watch anime cuz they TOTALLY f'd up Kei's look. D8 )

Anime Only (cuz I haven't read the maga yet. XD; ):
~Girls Bravo
~Karin (a.k.a. Chibi Vampire)

Both Manga & Anime:
~FMA
~Love Hina
~Azumanga Daioh
~Chobits
~D.N.Angel
~Fruits Basket
~Full Moon wo Sagashite