The Battle for Wesnoth - The Battle for Wesnoth is a turn-based tactical strategy game with a high fantasy theme.
TripleA - TripleA is a free (under GPL) turn based strategy game based on Axis & Allies board game.
FreeCiv - Freeciv is an open-source, turn-based strategy game based on Civilization II.
ThumbZilla - Awesome thumb stomping and kicking action game.
Sid Meier’s Civilization VI - Sid Meier’s Civilization VI is a Turn-based Strategy, War, Tactical, Single and Multiplayer video game created by Firaxis and published by 2K.
Warlight - Warzone is a customizable Risk-like strategy game where you compete with your friends to conquer the world.