Kingdom of Kroz
The original On-Disk hint sheet is mirrored on Theodor Lauppert's Homepage here.
Of particular note: On the title screen you can also activate a "Secret Mode" that starts you with extra Gems and other supplies. When the game asks you to select a skill level, press the exclamation "!" key (i.e. press shift-1) or press the letter "x", depending on which Kroz game you're playing. With Kingdom, Caverns and Dungeons use the letter "x" to activate the "Secret Mode", and on all other Kroz games use the "!" key.)