A bloody sci-fi take on chess, Warhammer 40,000: Regicide is currently available for 99p / 99c on the App Store.
While Regicide still features opposing pieces on a grid, here represented as Space Marines and Orks, its gameplay is more than your typical chess match. Special abilities let your forces unleash grenades and ranged magic, leap across the grid with a jetpack-enhanced leap, or deploy energy shields, depending on the unit. And taking a piece in Regicide is portrayed as a gruesome kill, whether it's a chainsword to an ork or a space marine exploding into a red mist.
Warhammer 40,000: Regicide's expanded version of chess and its richly tactical battles earned it a Silver Award in our review; to try its bloody chess matches yourself, you can find the game on iPad and iPhone.