Now that the event has started, I thought this would be a good place to list what hearts there are and what effects they each have, as a reference guide.
Feel free to add to the list below, and I’ll edit this post when I can, with more info. Also, feel free to give a rating for each, in case gearbox want to know what we liked and disliked, for future events.
Bro Love - Turns one enemy into an ally, temporarily (aprox 5 seconds?)
Sizzling lover - Explodes into a corrosive blast, applying DoT
Burning desire - Explodes into a fire blast, applying DoT
Wrong event - Releases ghosts (like bloody harvest event) - ghosts can drop terror weapons/grenade
Looty Boi - Drops loot
The big muscle - Increases Damage?
Just found this image. Might be more useful: