Minecraft wiki entry for Creeper, associated text: In a game called Quube Twodee made by Universal Chicken in Adelaide, Australia, one of the levels has a creeper face.
PixelJunk Shooter 2 for the PS3 shows a small creeper in the title screen hidden among other enemies native to Shooter 2.
In a Notch-designed custom level for VVVVVV, "Pyramid Escape", a creeper's face can be seen carved into the background to the far left of the pyramid.
In Torchlight II, the creeper appears in an uncommonly generated side area of Act III's Sundred Battlefield called "Notch's Mine". As expected, the creeper's found inside run toward the player and explode, leaving behind several dirt blocks. A chest at the end of the area can contain one of five Rare swords with their own unique attributes.
In a game called Strollin, there is a purchasable creeper item, which makes bombs throw the player farther.
In Geometry Dash, beating level 16 (Hexagon Force) on normal mode rewards the player a creeper face cube. This can also be colored to make it look like a normal one.