Must have unit?

This is my collaborative post for FTW on my must have unit/s in my army. I say units because for my Blood Angels army I always have two Baal predators. This is because of the sheer scare factor of two twin-linked assault cannons. Combining this with a 50% chance of getting over-charged engines means Baal preds can take the role of a moving pill box with mass horde killing potentual. They also serves a duel role of being able to knock out light armour when needed and with front armour 13 can soak up a lot fire freeing my other units.