Like things you did that you think nobody else did.
In GTA San Andreas I would RP as a truck driver. I would steal a semi, find a trailer, drive around on all the freeways from city to city, drive the speed limit, and make stops at stores and shit pretending I'm delivering a load.
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In Skyrim I glitched the game. So I had a character that was a werewolf. The glitch occured due to attacking my follower Serana until she would attack me with vampiric drain, and then I would blast her off a cliff or something. Now the glitch was that my werewolf got infected with vampirism. He could use the basic vampire powers as a human, but his stats wouldn't regen in daylight even in werewolf form until feeding on a corpse. Also I killed a dragon with this...thing?...