There is another random encounter... the
Unwashed Villagers.
The UW were the closest thing the Fallout games had to a clan. Their haunt, given Fallout 1 and 2 weren't online, was the forums on Interplay's website. Their stated mission in life was to ensure the forums stayed friendly, by chasing off flamers, n00bs and trolls.
Black Isle's staff, particularly Dave Hendee took a liking to the UW's efforts and their amusing alter egos, and gave them their own special encounter in Fallout 2.
The encounter itself consists of a dozen or so of the more senior Unwashed Villagers who have surrounded and are finishing off a 'pathetic flamer'. Each has their own unique description, and a combat taunt or two they shout out during the battle. I don't think you got anything cool for seeing the encounter (the UW all run off at the end) so it's just for fun.
I'm certainly not bitter because I wasn't included in the encounter, despite being the most prolific UW poster on the FO1 board after most people migrated to the FO2 board. No, definitely not.
*seethe seethe*