I posted the first mythbusters halo reach series video earlier this week, the second one follows up with some great tips.
1. you can survive any fall by landing on top of another player
2. you can kill another player with the impact of a grenade
3. tanks can be romantic
4. you cannot pummel through holograms
5. you can stick a frag grenade and send it off course with a plasma launcher (who could actually do this?)