Sarah Kerrigan said:
Big boobs and magic?
First thing that comes to mine is Witchblade. I would say that if you want big boobs and magic.
Yeah but it was an awful anime...
As far as boobs go...someone mentioned Ikki Toussen, you can't get enough boobs there.
Honorable Mentions:
Amazing Nurse Nanako
Cutey Honey
Burn Up (one of the series even had a Jiggle counter option where it counted how many times each girls boobs jiggled in the episode)
Gantz: Has its fair share of boobage
Goddanar: No magic, mechs but still lots of boob
Magical Shopping Arcade Abenobashi
Mouse: tons of boobage there, again no magic
Tenjho Tenge: much like Ikki Toussen
If you want actually good anime though, and not just magic/boobage, go for:
Trigun
Black Lagoon
Fullmetal Alchemist/Fullmetal Alchemist Brotherhood (the better of the 2)
Gurren Lagann, got boobage in there too, but it really is just an awesome anime.