Command & Conquer: Red Alert
Command & Conquer: Red Alert
The Counterstrike expansion pack added secret missions to the game that were called "It Came From Red Alert". The missions feature giant ants as the enemy. You can unlock this game mode in the PC version by holding shift and clicking the speaker in the upper right corner of the title screen. The game mode is also present in the collected version Red Alert: Retaliation but in the console ports you had to unlock the missions by beating the game.
Contributed by Mass Distraction