A Bantichrist is someone who manages to kill a conversation that has good banter. Their mere presence may create an awkward, perhaps even angry, silence.
Guy 1: "Hey, guys, knock knock!" The Bantichrist: "Someone get the door!" *Silence* Guy 1: "Ahem..."
A bantercheque is one persons recognition of anothers sucess. It can be anything from something as innocent as buying a DVD you wanted, or sleeping with the girl youve been buttering up for ages!!