Ultimate Showdown of Ultimate Destiny

Crossovers. We think about them a lot. We ask ourselves questions, like "What would happen if Doctor Who entered the Star Trek universe?", or "Who would win in a fight: Spider-Man, Sonic the Hedgehog, or the Teenage Mutant Ninja Turtles?" Someday, someone will create a crossover unlike any other, uniting the best of video game, cartoon, and comic book characters to see who will come out on top. And by "someone", I mean me. I am pretty sure that I know enough about each universe to effectively create a story that would do each series justice. If you think of any ideas for crossovers, please share them with me. I appreciate your input.