This was a quick, one day project I did today. It's a volcano with a crumbly floor that falls in pieces within seconds of stepping on it. The floor can also be destroyed by shooting it.
This is the helicopter at the top of the volcano, acting as the spawn room. It contains raycasted walls that (usually) stop people from shooting each other while in here.
At the edge of the volcano.
Looking down inside. There's a center platform that stays stable so people can jump down without falling straight into the lava, unless they miss it, which is quite funny to watch. There's a nice flare effect when someone falls into the lava, but unfortunately standing around to look at it will either have you suffering the same fate or being pumped full of shotgun bullets.
Looking up out of the volcano from the center platform inside.
The inside of the volcano. Each tile breaks away within 3 seconds of stepping on it, and instantly when shot.

Every time someone gets a kill, there's a 1 in 20 chance that a plume of lava will fire out from below and crash into the floor accompanied by an explosion, shattering the floor around it before falling back down and possibly taking someone down with it.
Similarly, every 1 in 50 kills triggers a massive plume to fire right from the center of the volcano, causing a very large explosion.
No that is not a propane tank what are you talking about.
And there you have it. The shotgun, bow, and pill are usually used. It's not really supposed to be pretty, I just tried to make it somewhat appealing so it wasn't just "you're inside a box with a break-away floor with lava in it". Now it's more "you're inside a volcano with a break-away floor with lava in it". You really don't need to see the outside, as it's only been detailed to the point that it looks appealing from the very short time you're outside while on the ramp from the helicopter to the volcano.
I'll probably post a save in the near future.