Well, that was a good one; plenty of drama and back-and-forth. Poor Jim's gonna hear a lot of not-exactly-subtle jibes at his weight, I'm betting.
For the next series, I've got a couple of ideas:
The Light of My Halos: With the Master Chief Collection coming out, you could speed-run one level from each game back-to-back (though that's pretty long for one of these videos), or pick a challenge to complete (for example, kill an Elite in every game, or grab a skull in each game).
Sunset Overdrive Clever Name: Set the clock for 5 minutes and see who can have the biggest combo by the end of it. Twist: you can't touch the ground, grinding only. The combo meter resets if you get shot, so that's an easy way to track it rather than having to rely on memory.