I posted this in another thread a few days ago.
I did a lot of research on this last fall and, based up the input of dozens of magicians, I came up with three gaffed coins/coin sets that cover a lot of ground.
Tango Ultimate Coin - hard to describe without giving away the secret. It does much of what a flipper, a slippery sam, and a shell can do. And it can do things that the other gimmicked coins can not do. The DVD comes with a bunch of good routines such as matrix, reverse matrix, coin penertations and a good 3-Fly routine. No reset required and only limited by your imagination.
A copper/silver coin. These are dirt cheap, there is no reset. Deceptively simple to do an in the spectator's hand transposition. Bobo's MCM has some really good routines for a copper/silver coin.
Copper/Silver/Brass Transposition set. I just got a Tango set. Comes with a centavo, a half dollar, a chinese coin, and a gaffed coin that is a mixture of all three coins. It's beautiful. The basic routine is good but I think you can be pretty creative with this set.