Wireworks might be the most unique tower defense game I've ever played, with you building up weapons from modules you wire up to different logic blocks.
Monsters are Coming! Rock & Road has just planted itself right at the top of my wishlist for the excellent combination of survivor-likes with tower defense.
Rift Riff is all about jumping through portals (okay Rifts, whatever) and extracting precious juice. Monsters don't like you doing that though but the juice must flow. It's out now with Native Linux support.
Cataclismo is a game where you design and build a fortress to face off against waves of enemy hordes. The LEGO-like building system is a lot of fun, really letting your creativity shine.
With an upgrade system that's a little inspired by the popularity of Vampire Survivors and all the games that followed, Rogue Kingdoms combines some interesting looking tower defense gameplay with direct hero control and roguelike elements.
If you love tower defense games, you're going to want to check out the new demo and trailer for the upcoming Rift Riff. A "strategically tight" game, the developer says.