Im an advocate for self executions... 5v1 and dont wanna get tea-bagged after you get downed? hold down both triggers and bumpers to pull your shotty or pistol up to your dome and go out on your own terms! you have to hold them for 3 seconds to complete the execution... during this time your character slowly pulls the gun out, with his arm all shakey
Maybe even have individual executions for characters... tai uses the shotgun like he did on the game (unless you switched it for another weapon... guess that could be a problem). And Carmine could slit his wrists all emo since thats the type of guy he strikes me as.