Gasoline trap. It sets the entire field on fire and can't be put out with water (because it's a gas fire), so anybody who battles who isn't Fire type gets burned. While it does not do any additional damage, it is a permanent stat until the end of the match. The catch is, it also cuts the user's HP by half of the maximum (like Belly Drum). It's the signature move of my hypothetical Water/Fire Pokemon, Dieselium.
Ice Age. Used by Ice types. At the cost of the user's life, it summons a permanent hailstorm that does twice the amount of damage a normal hailstorm does. The only way to stop the effects is with Rayquaza's Air Lock.
Thunderstorm. Takes two moves to set up, but creates a permanent thunderstorm that has a random chance of hitting somebody on the field with a Thunder (120 HP damage). Negated if somebody happens to have Lightning Rod.
Tectonic Shift.. Similar to Thunderstorm, but instead has a chance of setting off an Earthquake of Fissure at random times. Only avoidable by Flying types, obviously.
And, as an added bonus:
If, during a single match, people manage to use every one of these moves and then somebody uses Draco Meteor, it sets off an unavoidable move called Apocalypse, where the field blows up, everybody dies, and the match ends.