Anaglyph 3D glasses! You know, the game TrackMania actually has an anaglyph mode, and it never fails to surprise me how much it does help when trying to stick the landing on a huge jump across the track. That extra depth information may be subtle, but your brain will use it if it is provided.

Granted, after playing like that for an hour, I take my glasses off and the world's colors are totally wonky...

I seem to remember that Space Quest III came with a pair of Anaglyph glasses too. Came on perforated card stock in the box and you'd punch them out and put them together. I don't remember the effect working very well though, alas.

Man, those were the days, back when games came with neato stuff in them above and beyond the game itself. Big colorful manuals, buttons, postcards, real actual zorkmids. Ahhh, those were the days.