System Shock drove me absolutely bonkers when it first came out. Being used to Wolfenstein 3D and Doom controls, trying to figure out System Shock was such a tremendous chore that I nearly stopped playing it.

I'm talking a good 3-4 hours spent just getting the button layouts down and training my muscle memory so I could perform them without having to think. Once all the pieces clicked into place though, holy crap, that game (and its sequel) freaked me out in ways very few other games managed over the years. Excellent review, @deadspace! :)