The showdown between pirates and ninjas (also, robots and zombies) begins in earnest with the release of Pirates vs. Ninjas Dodgeball, a lighthearted celebration of long-dead cultures and non-fatal projectiles. The game and its 8-player online matches can be had for 800 ($10).
Similarly priced is Shred Nebula, which immediately defies expectations by being utterly devoid of guitar-playing space clouds. In fact, it offers "deep multiplayer space combat" for up to eight players online, along with Adventure, Score Attack and Deathmatch modes.
Finally, there's the online-capable and sufficiently self-explanatory Gin Rummy for 400 ($5). That about does it for this paragraph.