The original Shantae for the Gameboy Color. Looks more like a GBA game in every way
TMNT IV: Turtles in Time. Most specifically that they managed to cram the whole arcade game plus versus plus 2 additional stages into an 8Mbit (=1MB) Cartridge
Any game using the undocumented, because unknown to the developers of said card, 160x100 16 color Text Mode for CGA graphic cards on PC. Keep in mind CGA is supposed to have 4 colors max at once.
Speaking of PC, the 1988 french game Le Manoir de Mortevielle. Why? Because it used robotized speech (as in, the software reads the text and and speaks it) in it's game. Keep in mind the game is less than 1MB big
Any game developer who says the real time terrain deformation is not feasible on today's hardware should play both Magic carpet titles. They did it in 1995 and 1997 - completely in software without any hardware acceleration at all!
The Nintendo eShop rating Thread: http://gamrconnect.vgchartz.com/thread.php?id=237454
The Steam/GOG key gifting thread: https://gamrconnect.vgchartz.com/thread/242024/the-steamgog-key-gifting-thread/1/