Here's my Pico8 game 3D Wars.
It's a simple invaders game, with an added anaglyph (red/blue) 3d mode.
The anaglyph mode is very rough and ready. The red/blues aren't quite the correct hue (and as there's no way to hack the palette they just have to do). Also, because there's no blendmode natively available, it relies on persistence of vision to make it work. [ WARNING ] This means it is VERY flickery - if you're in any way sensitive to strobe lighting give the 3d mode a miss!