These can be purchased for ten Love Tokens each from vendors during the Love is in the Air holiday.
If dropped on the ground, they will taunt nearby mobs, making them a potential (but very weak) option for short-term crowd control.
However, their primary purpose for most players will be for completing the achievement I Pitied The Fool, which is a criteria for the Love is in the Air holiday meta achievement Fool For Love. To complete the achievement, you will need one Love Fool for each of the required locations (five total). Travel to the location, drop one on the ground, target it and type /pity for credit. As a tip, it does not need to be your own Love Fool to receive credit, so you can save on the Love Tokens cost by grouping with friends or hoping you get lucky by encountering another player in your random dungeon or battleground completing the achievement.