Halo 3 Deathmatch. I run up on my buddy and lob a plasma grenade at him. He dodges and the grenade bounces off the wall and sticks on my face.
We were laughing our asses off, referencing the episode of Red vs Blue where that one guy got the plasma grenade stuck to the side of his head.
"What? Like a spider? Get it off!"
"No, it's not a spider. It's blue. And fuzzy."
"What, like a fuzzy blue spider? Get it off!" *BANG*
lol's all around
Also, I wish I could post my favorite suicide video from Halo 3. I set up a shitload of canisters in a circle, stood on top of them (with canisters scattered randomly all over the floor) and tossed a firebomb grenade in at my feet. My flaming carcass flew about two hundred feet straight up, then straight down, where the physics engine clashed with the graphics engine and made my body approximately half it's normal size, with my head coming out of my stomach and my legs coming out of my lower back, but only from the knees down.