Lucky Spin is an achievement in some versions of Plants vs. Zombies that is earned when the player rolls three diamonds in Slot Machine. It is arguably the hardest achievement in any version of Plants vs. Zombies it appears in because even just one diamond is very rare, and three is even rarer. In console versions, however, they just have to get a single diamond. It will not give them anything, but two diamonds will give the player one. On the 1.02 update of the PS Vita version, however, the achievement does not involve diamonds to get it; instead, three of a kind in general will get it.
In the 2.1 update of Plants vs. Zombies 2, they were replaced with gems.
Before the 2.1 update, if a player killed a Treasure Yeti and got its lunchbox, they would receive a diamond. However, due to the removal of diamonds on the 2.1 update, the player does not get a diamond anymore, but instead a bunch of coins which total to 1000 coins, which is the exact value of a diamond.
In the Chinese version of Plants vs. Zombies 2, they are sometimes found in lucky cards in the older versions.
In Slot Machine, you will get diamonds for spinning on rare occasions.