Jacks or Better is among the most common video poker games. The player gets five cards, chooses which to keep, and is paid by the final hand according to a paytable. A pair of jacks or higher is the lowest paying hand. The paytable matters a great deal. The full pay version, often called 9/6 because a full house pays 9 and a flush pays 6 per unit, returns about 99.54% with perfect strategy. Versions that pay less on these hands return noticeably less.
Example
On a 9/6 machine with perfect play, the long run return is about 99.54%, a house edge of roughly 0.46%. A 8/5 paytable of the same game returns less, around 97.3%.