Not technically worst gameplay-wise, but worst dev-philosophy-wise, but I'll nominate Dungeon X: Flesh Wounds, from the 2013 7DRL challenge. The gameplay itself wasn't too bad, and it had great artwork, but it was billed as a 7DRL, and what we actually got was a flashy tech demo for a future commercial project! (Wonder what became of that?) Yeah, that's not exactly what a 7DRL is supposed to be... Granted some 7DRLs do go on to be commercial or freemium games (such as Hoplite and 868-HACK), but the devs didn't plan this (it just happened due to the game's popularity), or at least didn't make it so blatant that they were doing this. But to use the challenge as an advertising platform is just... shameful. Oh, and they made all their art assets in advance, specifically for this project. Yes, I know the rules technically say it's just the *code* that needs to be written during the challenge (and even so you can use previously written code so long as it wasn't written specifically for your game), but this feels like bending the rules a bit TOO far, given the amount of effort they put into it...