While Best Buy might not have quite the used game selection as say Gamestop, they have amassed a pretty solid collection over the years. As a result, they have brought back a sale that is a favorite of many, buy two get one free on all pre-owned games.
As with all other buy two get one free at Best Buy, the free game is the cheapest of the lot, so it makes more sense to get games that are around the same price. This sale is also available online in which you can look through all the games right here.