Remember the rubber pencil bending illusion we all used to play in school?
You bring out two Sharpies and give one to your spectator and follow your actions.
You start waving the Sharpie in your hand and create the optical illusion that it is bending as if it is made of rubber. You ask the spectator to play along and do the same.
As both of you are enjoying the fun of it, you slow down and somehow you end up with a Sharpie that is really bent! It's a real Sharpie and it can write too! Do this little quickie as an ice-breaker then use the bent Sharpie to sign their cards for your next effect!