Tower Defense

Sanctum is a 2011 video game that combines the game styles of tower defence and first person shooter. The game runs on the Unreal 3 engine. Coffee Stain Studios was one of the main contestants in the 'Make Something Unreal Contest' by Epic Games in 2009 with the title Sanctum, at that time unreleased.They were among the top runners in the categories of: "Best FPS-game mod", "Best game mod" and the educational category.

Gratuitous Space Battles (GSB) is a video game developed by the UK-based company Positech Games. It was released on November 17, 2009. On one level the title is a space battle simulation consisting of a number of engagements between two opposing fleets of ships. While sometimes assumed to be a real-time strategy (RTS) game based on screenshots, actual gameplay focuses on the setup prior to the battle, making it play more like a tower defense game.

Defense Grid is a 3D singleplayer tower defense game. You must construct defensive towers of various types on predetermined areas to get rid of incoming alien swarms before they reach your mainframe and run with its power cores.

Demigod is an RTS/RPG/Tournament Fighter hybrid developed by Gas Powered Games and published by Stardock. The game is almost entirely multiplayer based with singleplayer consisting of skirmishes and tournaments against AI opponents. Using "assassin" demigods, players are treated to a Diablo-esque RPG game with RTS elements, while using "general" characters results in an RTS game with RPG elements.