Common issues that I know of:

Monitor refresh rates. I could detect the flicker at 60Hz, was very annoying at times. Wouldn't think that this would be a problem with LCDs though.

Strobing. Flashing adverts, game effects. Sometimes these can trigger seizures and other ill effects.

Parallax problems. Early 3D games sometimes had parallax issues, I think Wolfenstein 3D was one of them. I knew a few people who got nauseous playing that game.