Futzi01 has released yet another completed pony game, this time focusing on single player tower defense as opposed to online battle. Each character has abilities similar to their Pony Tactics style, with Twilight bombarding with AoE artillery, and Rarity sniping. As is the norm for Tower Defense these days, each one can be upgraded for extra range, faster attacks, or higher damage.
Head on over to this page to play it! With three maps, it should give you something to do for the afternoon while sitting in Mann vs Machine queues.