Marvel hasn't had too many "tag team duo's" in comparison to DC. Unlike DC, most of their Golden Age heroes vanished for ages aside for Captain America and they're more about solo heroes and teams.
Off the top of my head, some famous "Marvel Buddy Teams" have been Luke Cage & Iron Fist, or Beast & Wonder-Man.
As for "World's Finest" worthy, some people may cling to a Cap & Thor thing, but they're more Founding Avengers than a "duo". How often did they team up without the rest of the Avengers there? Sure, Cap was one of the few mortals that Thor respected in the beginning, but I'm not sure it is the same.
Spider-Man & Daredevil come close, especially in recent years.
Kind of a shame that Spidey wasn't taken under Cap's wing a little during his run at New Avengers. Y'know, some training, etc? I mean Spidey's always looked up to Cap, but on NA we saw none of that. That's just one of the many problems with that title. We're supposed to buy them as cohesive characters interacting, but little of their interactions were beyond "jokey one-liners" or plot-centric dialogue. Where was, say, Luke & Peter discussing their shared perspectives on being heroes, husbands, and possibly fathers? I'd rather see THAT for pages than just yet another "Spider-Woman is hot" cheesecake spread.
Practically speaking, though, it's probably Spider-Man & Wolverine. They have teamed up a few times over the years and have clashing senses of morality, with Wolverine having little qualms about killing someone if he had to, and Spider-Man being utterly opposed to it (although he got over "accidentally" killing Charlie back in SPIDER-MAN VS. WOLVERINE #1 aweful fast, and he has tried to ice Osborn when he's snapped a few times, and let's omit the Other face-eatin'). Even their last spat of MTU appearences sort of show some of this dynamic. They even had a SUPERMAN/BATMAN esque mini a while back, and I'm frankly surprised Marvel has gone this long without making a SPIDER-MAN/WOLVERINE ongoing; in sheer terms of no-brainer franchise milking and fan pandering, that's, well, a no-brainer.
Just my thoughts on the subject.