I'd say Ratchet and Clank as my main and Jak and Daxter as my partners. A team that I would be afraid of however would be Dante and Kratos, arguably the two most powerful characters that have been revealed so far. To this day they're fan-bases can't agree on which character is stronger, just look in the Dante vs Kratos thread in this forum for proof.
By the way, just call me Count for short.
Ratchet & Clank, and PaRappa The Rapper is my team so far. If Sir Daniel Fortesque is announced, he'll definately be on that list as well!
Dante and Cole McGrath seem to look like the two biggest power houses in the game so far, and would probably be a devestating team based on they're Level 2, and Level 3 Supers.