My worst experiences would probably take up several pages.
My best would be a tie between two games:
In my first online Mafia game-my only previous experience was a few games of a simpler, card Mafia played at a convention,-I was the FBI Agent. Every other turn, I could investigate a player and learned their role. I created an alliance with the other good guys. One of the other Town players joined up with some of the other people who were unhappy that a newcomer was playing actively and tried to get me lynched, AFTER it was confirmed I was a good guy. Despite this, I successfully eliminated the Mafia, leaving behind instructions that led to their downfall after by retconned death in the last turn. Won MVP for this one.*.*
The second was when I was the Godfather. I was steal dealing with players who had a grudge, but managed to survive until the last round by weaving an impressive web of lies and using everything I could to stay alive. In the end, me at the Detective were the final two players left alive, and I won due to the decision of a tie-breaker. It was a pretty epic way to end things.