A.K.A. Wearing pieces of different-colored/polarized plastic on each eye to trick you into think stuff's not just a flat image on your computer screen, but is actually happening, assuming you weren't already deluded enough into thinking it already was actually happening. Sometimes ruined by nausea and the breaking of the illusion of immersion by your landlord/parents/siblings/roommates/little goblin in your brain yelling at you.

I would put this in Suggestions but I can't remember whether or not there's already a way to do this without the game needing any patches/changes. Post your preferred solutions here! And be on the lookout for any that implement the use of the ubiquitous dinky little red/cyan glasses, because those are the only kind I have on me at the present time.