Halo 2:
Coag, I'm in a Wraith somewhere in the centre (though still near my base) and I see a Banshee flying towards the other base, with an enemy in it. I shoot, he exits the Banshee and both he and it drop down the hole in the roof. Then, I see my shot disappear into the same hole. A moment later, I see the Banshee exploding and got a kill
Another in Halo 2, Relic, Slayer with random weapons (or swords, I can't remember) at start. Start of the match. I spawn near the Ghost at the Relic tower, enter and run half a lap or so around the Relic. I suddenly round a corner and see two people walking straight towards each other with swords drawn, they hadn't noticed me. I slam the booster and WHAM, double kill. And first blood. That was awesome
Team Slayer, Turf. It's chaos in the main street, weapons dropping everywhere. I run to the Warthog at the end, hop into the turret and get a killing spree before somebody pops a rocket and totals the 'hog.
Not really a kill, more like a technique. Slayer, Midship, Shotgun/PP. Everyone is running around with charged plasma pistols, the n00bs generally with shotguns (I only play at LAN parties with a fixed group of friends). So everyone is popping each other's shields with the Pistol and then meleeing or switching to shotgun, but I'd thought of another tactic - run up, shotgun from some distance away and if they're not dead (which is usually the case) melee them and get an insta-beatdown/assassinate. That was one of my better games. Ahh, good times.
Attempting to snipe someone who's moving left and right on a ledge, and missing four times in a row. XD
First time I ever played Halo. Team CTF, Terminal. I somehow managed to get in a Warthog and I'm driving it around in some small courtyard, running into stuff all the time. Then my team's flagcarrier attempts to run through the courtyard into our base to plant the flag..... Let's just say, that was the first CTF point I ever made
I'm not sure about this one - Co-op, the level where you have to kill the Heretic Leader and he pops two holograms. I remember flailing at one with my sword a few times, and then suddenly we get a cutscene. Again, I'm not really sure about this one, since I believe the guy goes active camo? still, that was pretty epic, accidentally ending a level after less than ten seconds XD