One Week is about a couple that's having a fight, so I don't think it works all that well for Sam and Max. Although...
How can I help it if I think you're funny when you're mad
Trying hard not to smile though I feel bad
I'm the kind of guy who laughs at a funeral
Can't understand what I mean?
Well, you soon will
I have a tendency to wear my mind on my sleeve
I have a history of taking off my shirt
Max? Not that he wears shirts, but...
I've been looking for a good friendship song for Sam and Max, but so far all the ones I've found are too sappy. I might check the NaNoWriMo forums, they seem to have a lot of threads about music that works for specific situations.
I like to pretend that Just For by Nickelback works for Max when the player makes Sam cry in Hit the Road, and when Sam is in Hell in What's New Beelzebub?, but I'm mostly joking. Mostly. He does seem pretty protective of Sam.
I might think of something more later.