My friend got invited to a custom like this the other day, he said that there was an AR that fired tank shells and a plasma rifle or something that spawned Banshees. Some Halo 2 classics right there, sounds like Reach mods have really come a long way.
For some reason I assumed he was describing some chaotic meltdown in a matchmaking game. But if it was modded then yeah, I could see that. This will be a totally off-topic digression but anyway... back when the first Halo came out on PC, I got myself a hex editor and started modding like crazy for a while. The best stuff I did was re-skinning maps and replacing their sound files - I made versions of Blood Gulch and Death Island that were snowy like Sidewinder, and had the same eerie sound effects, and I also made a Blood Gulch that looked like the surface of the moon and had very low gravity. But the kind of stuff described here, I also did a lot of. First thing we tried was replacing AR bullets with rockets. That was hilarious for five seconds, then hilariously laggy, then just annoying. Replacing bullets with ghosts and stuff, and also braindead spartans that just stood there, that was really fun too - that's how I made wacky screenshots like these: Spoiler My finest work though was replacing a shotgun's pellets with sniper rounds. Anyone remotely in your field of vision would get instra-fragged at any range. Freaking hilarious on maps with lots of tight turns like Damnation.
I apologize if I'm off-topic, that's not my intention. I have a feeling it was a chaotic meltdown, not a mod. This happened during an online multiplayer match, it was not a custom game.
It would be nice if people were a little more forgiving. I was driving around BTB Asphalt on a Ghost, and fishtailed into a guy on my team. I never saw the guy and he was killed. I got a betrayal and was subsequently booted from the match. I was so mad, I stopped playing for about an hour.
Yeah, that's the crazy part. Stuff like you describe can happen in modded customs but shouldn't happen in multiplayer. If you can get clips of this online I'd love to see it - sounds wild.