As a fan of post-apocalyptic gaming, Twilight 2000 was one of my defining RPGs in the early 1980s. I played 1st edition for years and used the system for other post-apoxy games, like The Morrow Project. I avoided 2nd edition, mainly because I didn't like the system.
One of my favorite parts of running T2K was the NPC motivation system, a simple way to develop NPCs using a deck of cards. This was a very cool feature, one that I've mentioned before on this blog. Each suit focuses on a different core issue: violence (Clubs), Wealth (Diamonds), Fellowship (Hearts) and Power (Spades). The value of the card determines the strength of the motivation: 2-4 (low), 5-7 (medium) and 8-10 (high), with the face cards and Aces as special cards. For example, Clubs range from Murderer (Jack) to Stubborn to Brute to War Leader (Ace).