Another great gag used by Dave Bonsall in his working act, can be used in many different situations where you ask a spectator to hold their finger in the air, you then say, “just hold your finger here” ...as you reposition their finger, you bend it slightly and the spectators hears a sickening, bone crunching crack to huge laughs and "OOOHS!" even better if you then move the same spectators finger again in a later routine and it happens again. Dave Bonsall uses this during his knife through finger routine and then again on the same spectator during Crazy Mans Handcuffs.
The neck cracker's sometimes take a little wearing in before they give a really good crack, so once you've brought one, give it at least 50 or so cracks to wear it in. Occasionally it takes more.