I'd say Mario and Master Chief. They're the biggest icons I can think of, and if we only get one per company, it should be the most well recognized. Might bring more attention to this game, too. And they both have some pretty sweet jumping skills.
Rival Cutscene would be easy:
"It's-a Me, Mario!" "You look weird, you must be a Floods! Die!"
"The best things in life must be taken... by force!" ~Captain Khan