I think that's one of best memories from Fallout 1. I had to use some drugs to beat the thugs. And afterwards my int dropped from 7 (or 8) to 3. I came back to talk with the guy to get the reward, but my only chat options were like "uhhh?", "grrr" and "wooo!". That was insanely realistic. I loved fallout just for this.
Also when I took some other drug to boost intelligence the chat options changed, and suddenly I was able to talk some other guy into doing some strange stuff. That was awesome!