The Battle for Wesnoth - The Battle for Wesnoth is a turn-based tactical strategy game with a high fantasy theme.
Particlescape - Particlescape app lets you create stunning patterns at your fingertips.
Kingturn RPG - Mangobile - Mobile game developer focused on turn-based strategy RPGs for PC, iOS and Android
TripleA - TripleA is a free (under GPL) turn based strategy game based on Axis & Allies board game.
Advanced Strategic Command - Advanced Strategic Command is a free, turn based strategy game.
Fluid dynamics - Fluid dynamics developed and published by Reinder Nijhoff.