Nightmare Fuel / Poker Night at the Inventory
Max is the source of three of these.
First, his zombie exclamation of "Cheeeeeck!"
Secondly, the "Max and Crossbones" table. (A hint for this one: The Devil's Playhouse Episode 1 cliffhanger.)
Thirdly, "Make a calm and rational decision!"
"I. Do. Not. Lose."
There's also Heavy flipping the table in rage if he loses a hand, revving up Sasha and screaming in anger before the reveal that it was an Imagine Spot, with him plainly telling you to deal him a new hand.
Tycho's Slasher Smile, especially with lines like "That'll do, cards. That'll do".
Heavy's favorite story about a BLU Engineer and his wrench. Even the other players are creeped out!
Heavy: I am reminded of time when Engineer kill my entire team.
Damn, Heavy. That's...um...
. I'm...sorry to hear that.
Heavy: I search entire base for him. He tries to kill me with Turret and Mini-Turret, but I crush his toys like they are made of paper!
Strong Bad: Sound-a like-a some crappy toys, if you ask me.
Then I find him, hiding by Teleporter. I take his Gun away from him. He tries to hit me with Wrench. Haha! I take his Wrench, and then
shove it down his throat
all the way to the handle
Strong Bad: ...that is some [bleep]ed up [bleep], man!
Also, he never specifies what wrench the Engineer was using at the time, but it could have been the Southern Hospitality.
The look of horror on Max's face when Heavy finishes telling the story. It says a lot that is horrified by something.