The $2.50s are made special for paying the 3 to 2 payout on a blackjack. You won't find them anywhere but the blackjack tables. Some casinos really object to selling them. You might instead sometimes find 50¢ chips on blackjack tables, also used to pay that odd $2.50. 25¢ chips would be on the quarter or 50¢ craps game, maybe sometimes still on a table because they used to have quarter craps. Sometimes you'll find oversize baccarat chips, but sometimes only on the high roller baccarat table. Sometimes there's special chips on other games, like this $11 Red Dog chip at Fitzgeralds. You might find special chips in the poker room. Sometimes you'll only learn about promotions that get you special chips, like win cards, by asking at the player's booth. Ya just gotta look around!