Can't think of any from 3 or Reach (I bought ODST pre-owned years ago but only played Firefight and hated it so I gotta play campaign sometime) so the only one on my mind right now is from 4.
It was when I threw a frag at an enemy hiding on the bottom level of Solace but it bounced off the back of my team mate's head (he was walking in front of me) and managed to somehow kill two others in that same area that I didn't see due to them standing right up against the wall.
Wish I knew how to save videos to Theater at the time. --- "If you don't like something, don't watch it again. Why whinge about it on a forum to a load of divs? Don't worry about it." - Karl Pilkington
Only one I can think of was when I was playing Reach with a friend and was going on a killing frenzy. Some teammate in a banshee betrayed my friend and the empty banshee fell from the sky and splattered me, saying that I committed suicide. I was pissed at first, but we had a good laugh afterwards. --- Keepin' it classy.
One of the top ones though is when a friend and I were playing ODST and were on the last part of Romeo's level, and a dead Banshee hit me and sent me flying off the building. --- Not changing this sig until a Halo 2 remake is announced. Started November 2nd, 2011.
CEA: Grunt sticking another Grunt causing a chain reaction death explosion! I used the Grunt Funeral Skull too! 3: Somehow stuck my teammate across Narrows using the lift. Also killed an enemy so it was a Betrayel Kill. ODST: Got launched by a Brute Chieften onto an awning then imedeatly sniped in the face by a Jackal. Reach: Revenant pinball action around Hemmorage before exploding. 4: With active camo on Ragsnrocks (what I call Ragnarok), I get splattered by a teammate on a mongoose from our base lift. 4 Campaign: Playing with a friend on Infinity, doing the tank section. He goes to the elevator while I'm behind. The roof collapses on me, I go flying at Mach 9 speed, spinning like a bat outta hell, upside down, out of the area, then exploding a second later. --- Halo K/D. Means nought to me. Now, *HONK HONK* let's ride! *off into the firey explosions with the Warthog*