The Roof Tumbler: Shoots the enemies at the front of the garage the second everyone spawns, making the other players (as well as him) an easy target as no one is in cover.
The Resurrected - Lucky Shot: Player using a team life as he died from an NPC with a lucky shot, often depleting their whole health bar with a few shots.
The Resurrected - Twice The Coming: When two players die at the same time despite only having one team life.
The Resurrected - Dead Upon Arrival: A player who dies, uses up the only team life and dies within seconds of coming back. Will often see his two death notices on the screen if quick enough.
The Store - Back Shot: While robbing a store, a player may come in and shoot you, thought as "protecting" the store.
The Store - Casual Casualty: While robbing, a player may come in and confused at what may be taking place. They will either run out of the store or, in very rare cases but still plausible, go up to the clerk who has his hands up and do the "thrust" animation next to them. The player robbing can also shoot the player in fear of safety.
The "Let's Bang" Variations:
A player notices you play as a female character and, may or may not think you're an actual female, begins thrusting your character. Mic usage is optional but follows the line of "you a girl?", "you're hot", "bitch, you nasty".
A player makes the "thrust" animations on your character, male or female, just to pass the time. Usually while waiting for the package to be delivered in Rooftop Rumble.
A player will climb on a ledge and motion you over and ask you to crouch to give the impression of giving fellatio.
The Killing Time Killer: During waiting in Rooftop Rumble, this player will hop in a car and proceed to run you over and try to kill you even if you're not doing anything. Quite annoying as you'll spawn in Grapeseed and not near Rooftop Rumble when entering freeroam.
Hope I didn't add any that wasn't there already. Good thread.