I like it when the players are "in on it".
I played in a Star Wars RPG where we were scout troopers for the Imperial Star Ship Hornet. Basically, like the evil Enterprise in the "Mirror Universe" episodes of Star Trek, our mission was to seek out new new civilizations and enslave them to the will of the emperor, in the name of human rights -- that is the human manifest destiny to dominate all other inferior life forms!
It was fun for a while, but we didn't restart after the TPK.
Anyhow, in general, I like the idea of cogs in an evil machine, who think their cause is good -- when the players know the cause is evil.
No shades of gray are needed (strictly optional) and there's no tricking or railroading of players.
It also opens up the possibility for conversion to good guys when evil gets boring (which usually doesn't take long), and for dramatic tension until they decide to go good. Great, great start for a hero. I'm thinking Han Solo (once of the Imperial star fleet, then a mercenary, and finally a hero), Te'alq (once First Prime of Apothis, turns to join Stargate Command, eventually leads his species to freedom), Saint Paul (once a Roman official, then a convert helping the poor Christians), etc.
I played in a Star Wars RPG where we were scout troopers for the Imperial Star Ship Hornet. Basically, like the evil Enterprise in the "Mirror Universe" episodes of Star Trek, our mission was to seek out new new civilizations and enslave them to the will of the emperor, in the name of human rights -- that is the human manifest destiny to dominate all other inferior life forms!
It was fun for a while, but we didn't restart after the TPK.

Anyhow, in general, I like the idea of cogs in an evil machine, who think their cause is good -- when the players know the cause is evil.
No shades of gray are needed (strictly optional) and there's no tricking or railroading of players.
It also opens up the possibility for conversion to good guys when evil gets boring (which usually doesn't take long), and for dramatic tension until they decide to go good. Great, great start for a hero. I'm thinking Han Solo (once of the Imperial star fleet, then a mercenary, and finally a hero), Te'alq (once First Prime of Apothis, turns to join Stargate Command, eventually leads his species to freedom), Saint Paul (once a Roman official, then a convert helping the poor Christians), etc.