Awesome Games Done Quick is back again and running Halo again. Halo 4 is the pick this time and it's slated to be run around 9:00 PM EST this Thursday (January 7th). Here's the schedule, it changes a bit as games are finished.
AGDQ and SGDQ are semi-annual speedrun marathons for charity. The charity this time around is the Prevent Cancer Foundation, an organization founded 30 years ago this year to work towards preventing and averting cancer of all types. GDQ's have been known to raise over a million dollars ($1,000,000.00) for their cause over a single marathon, but they could always use your donation.
If you don't like Halo 4, they're also running a bunch of other shooters, Megaman games, Castlevania games, Mario games, other platformers, even tool-assisted speedruns which... are a thing to behold, they break the game on a level beyond what a normal speedrun does (which is usually a lot).