Hm, maybe Spider-Man and Mister Fantastic. Spider-Man can sense all the possible dangers, and Reed can deal with them using his brains.
If those two ever teamed up... it would be fun to read (read / Reed !!Anyone...? - oh never mind 😛).
And before I forget, it's a bit off topic, I know, but the coolest duo is Calvin and Hobbes.
Ironman and Spiderman. Spiderman would be perfect in a setting where his teammates could fire right at him while hes fighting the bad guys. With his spidersense working spiderman could navigate through ironmans blasts while he is pounding on the enemy.
Hulk and Herc. I'd love to see Hulk get another 100 class to pound with.