Blackjack...
Specifically, the deck. Removing one or more ten-value cards and/or Aces from the deck can dramatically increase the house’s edge, and few players will notice the difference between a deck of 52 cards and a deck of 48, or even an eight-deck shoe from which half a deck has been removed... buuuuttttt…
What if the machine shufflers arrange it so that many of the 10-count cards are at the end of the shoe, behind the cut card? Isn’t that the same thing as removing them to give the House a huge advantage?
Let's say that the machine shufflers put an above average number of 10-value cards in the middle of the shoe. By default, most people cut the shoe in the middle too. Now, the dealer places the front half of the cut to the back and puts the card in about a deck's worth from the end. Now, there are a higher than average amount of 10-value cards that are no longer in play - thus, giving the House a HUGE advantage!