Most nightmare-inducing character ?

[Beardy]

Voldo is a bit scary when he does that backwards scuttle thing. I'd be frightened if I saw him in real life.

I don't think I've ever had nightmares from games. I have had a LOT of that weird thing when you're dropping off to sleep and you can't stop seeing whatever you've been playing. For me, it's probably been those green shapes that dodge your fire in Geometry Wars Galaxies.