4th Edition Dungeons & Dragons‘s modularity makes it suitable for many genres: the modern era, Spelljammer, and even the gonzo mutant future of Gamma World.
For those unfamiliar: Gamma World was a D&D post-apocalyptic setting that included grenade-throwing rabbit-men, sentient plants, and crumbling radioactive cities. It’s a wonderful, ridiculous potpourri of post-apocalyptic elements. Gamma World 4E updates this with D&D 4E’s mechanical approach.
A lot of people dislike 4E’s mechanics for being “too much like a board game.” Fortunately, Gamma World is ideal for such mechanics, since it involves skirmishes between groups with a wide variety of weird weapons. 4E models this world cleanly and beautifully.
I ran Gamma World using one of the scenarios provided in the book, The Steading of the Iron King, which involved infiltrating a closely-held compound of Usagi Yojimbo knock-offs. I ran it as a Google+ Hangout using the Tabletop Forge add-on, which handled all our maps perfectly.
We had a great time, blazing away at bad guys and dealing with cramped passages. It’s light entertainment, with plenty of options and a gonzo tone.