As Six-y Beast enters the battlefield, you secretly put six or fewer +1/+1 counters on it, then an opponent guesses the number of counters. If that player guesses right, sacrifice Six-y Beast after it enters the battlefield.
Near Mint - $0.20
Near Mint Non-English - $0.20
Lightly Played - $0.20
Lightly Played Non-English - $0.20
Played - $0.10
Played Non-English - $0.10
Heavily Played - $0.10
Heavily Played Non-English - $0.10
Damaged - $0.10
Damaged Non-English - $0.10