Have you ever played Worms (World Party / Armageddon)? Hedgewars is an open source project to recreate the Worms games (even though they never come out and say it on their page), and they're doing quite a good job of it.
Each player gets a team of hedgehogs, and and arsenal of weapons. More weapons open up as the round goes on, and the last team with hedgehogs standing is the winner. Of course, it's hard to keep them standing when they could be taken out at any moment by bazookas, shotguns, grenades, air strikes, drill rockets, kamikaze hedgehogs, or cake bombs. And that's just a few!
What sets this game apart from other artillery games is a greater emphasis on movement. On your turn before you fire, you can walk, jump, ninja rope, teleport, dig, and even make new floors with girders. There's also one other thing this game has that Worms doesn't: Hats. Each member of your team gets not only a name, but also a hat! (and it's relatively easy to add more hats too.)
The game is perfect as a hot-seat party game, with up to 6 players on a single computer, but there is also smooth online play as well. Either way proves to be a fun way to play.
The team is still actively working on adding features to the game, so don't forget to check the author page for updated versions. Also, the version for download above is the windows version, but being an open source project, there arelinux and mac verisons available on the homepage.