The best burgers are the ones friends make for you on the grill.
But... IMHO In and Out top them all. I won't NOT make a special trip to have one but if I am out in California or Vegas I will make it a tradition to have double meat, fries (I ask for them well done) and a COKE (OK, In and Out does not have PEPSI and I'm not going to sneak one in.

)
I'd love to try the parking lot shuttle to the In and Out at LAX thing with someone sometime.
With apologizes to some Flyertalkers... I had White Castle ONCE and sober... and got very bad food poisoining. The smell of them and the look of them make me sick.
The only other fast food I'll make an effort to get is Chick Fil A.