The set of '86 slot tokens issued by Harolds Club in Reno is one of the hardest to assemble. Seven tokens, each with a letter of the club name. A, O, and D are the tough ones. These were mixed in with common tokens in the machines. Turn in a complete set and you got a prize. I've forgotten what it was... not much compared to the scarcity of the set today.

Also, most of the first-year slot tokens of Nevada are scarce. Osborne and Michigan Tool for example, made some of the earliest in 1964-65 when US silver dollars were about gone and private issue tokens were first made legal. All the silveen and goldeen tokens are scarce. Many of the later sterling and fine silver presentation tokens are also low mintage and scarce.

The holy grail of tokens though, has to be the Harrah's $1 token struck in platinum for Bill Harrah. Only one exists. It was included in the Platinum Collection that sold on eBay in 2005 for $1 million. The Pt dollar would be worth over $1000 just in precious metal value; collector value would be a multiple of that.