Scotch and Soda
We suggest the Magnetic versions of this gaff because they are easier to manage and easier to nest silently. There are versions that "click" into place and use what's called a bang-ring to disengage. Once locked into place you must use this tool to get them apart. In our experience, the magnets pass a brief examination by a spectator and are easier to get apart during reset.
It's interesting to use this effect in dollar size because it's more visible for larger audiences.
We usually prefer real coins to poker chip gaffs because the coins have a nice sound to them, when metal touches on metal. But these poker chip versions are quite attractive, and in the right circumstance, would look great.
Tip: get a bang ring!
A bang ring is an inexpensive, but very worthwhile little tool to help loosen the coins in a Scotch and Soda set.