Best Fast Food Burger: In-and-Out. No contest. I'd say Fatburger was a good distant second, except I'd be lying because Fatburger is horrible.
For South Pasadena (real limited area, I know), I'm gonna go with "Hi-Life" on Fair Oaks. Awesome bacon cheeseburgers, and the "small fries" and "small onion rings" basically come in a wheelbarrow. Or maybe it was a U-haul trailer. All I know is that I've never actually been brave enough to get a large order.
For a quirky burger, I'll hit up "Burger Continental" in Pasadena, which actually specializes in... Middle Eastern Food. Complete with belly dancers. But, the burgers are generally pretty good. I had a San Francisco burger once with onions and shredded cheddar cheese. The patty was like 1/2 lb and was oval-shaped and it was served on a sourdough french roll. Good eatin' (but not as good as Hi-Life).
In Hollywood, I'm headin' over to Carnie's on Sunset. Burgers and hotdogs served out of an old Railroad car. What else do you need?
I hear "Father's Office" on the West Side has good burgers, but I've never been so I can't comment.
And, lastly, my DM, known on the boards as "setanta", grills a damn fine burger. I always look forward to a "Game Day & BBQ!" e-mail from him or his wife showing up in my inbox. My wife and I always know we'll be in for a treat when we see one of those.