There was a rumor one time that the Survival mode for D2 was going to be based on extreme high heat and / or a hurricane that hits DC. In all honest when they announced going back to NYC I figured this was where they were going to add the Survival mode but alas.

Aliens vs. Predator on the PC from 1999, the entire Marine campaign, and alien campaign when you had to start fighting the Predators. I had nightmares from this game. Also, Jurassic Park 2 Chaos Theory on the SNES from 1998, the game was stupid difficult and the Raptor Attack mission still puts me on edge.