Here are some Marvel team-ups I'd like to see. Either as a mini-series or bringing back the Marvel Team-Up title where it's not just Spider-Man and somebody else.
1. Psylocke & Elektra - this kind of seems like a no-brainer to me. They may have actually had these two face-off already but if they've never done it, I'm surprised. It seems like a perfect match up and it would be cool to see them work together.
2. Iron Man & Crimson Dynamo - we've seen the two fight each other but I'd like to see a kind of reluctant team-up ala Red Heat. Something like terrorists target both countries and they have to work together to stop it. Iron Man is the good cop to Crimson Dynamo's bad cop.
3. Human Torch and Iceman - why aren't these two featured together more often? They seemed like despite the vast difference in powers that they'd make great friends. Both roughly the same age and similar personalities. The dichotomy of their powers working together would be cool (no pun intended) to see.
4. Sentry and Moon Knight - I know this sounds out of left field but I have this thing where I'd like to see Marvel's closest versions of DC heroes do similar stuff and Moon Knight is the closest hero Marvel has to Batman and Sentry is probably the closest to Superman.
I have some others but let's see if anyone else has a team-up they'd like to see.