Short for 'swagger vampire' - someone who is a complaining buzzkill, never has anything positive to say or counters any good point with some sort of oppositely negative statement and/or hypothetical scenario. A hater; a crybaby.
Stop being a swagvamp, you know my gators are fly.
When we were at the game, you couldn't stop complaining it was cold out. You were a horrible swagvamp.