I always use one for live play (online its a matter of taste). I almmost had a hand mucked by a dealer once, which cured me of being inattentive.

I have two silver $0.50 pieces, an Aladdin $1.00 Token and a Hollywood Club $1.00 chip in an air-tight which I pull out as the whimsy takes me. No superstition just whichever comes out of my Pocket first.