Game Zone
Welcome to Pasadena - I live in South Pas now, but close enough...
I recommend Game Zone on Colorado as well. They're really the only "full service" shop around. They've got a decent selection of d20 stuff, a bunch of old 1E and 2E D&D stuff, GURPS, LOTR, most other RPGs, Wargames & miniatures, and of course TCGs. They also have an okay selection of wargames and even some family/party games. There's also a pretty big computer gaming section in the back that always smells like sweat and stale pizza.
The one down-side is that the store is not very well lit or organized, but that's kind of the fun of it - whenver you find what you're looking for, you feel like you've discovered something that no one else knew was there.
The Borders on Lake Avenue between Del Mar and California also carries some D&D and d20 (mainly SSS) stuff.
For a bit of a drive to the north-east, you can try Last Grenadier in Burbank
http://home.earthlink.net/~danielc/tlg.html
I personally wouldn't bother with the Game Keeper - their selection of d20 stuff is almost non-existent.