Dean- Minion; you are adorable when you imitate the minions from Despicable Me, so he calls you minion.
Sam- Short stack; he's a giant. Why else?
Castiel- Honeybee; he loves the honeybees.
Adam- Sweet pea
Gabriel- Sugar
Lucifer- M' Lady
Crowley- My queen
Michael- Sweetheart
Sammandriel-
Chuck- Hun
Kevin- Creeper; you are very stealthy
Ash- Zombie; you look like one in the morning.
Gadreel- Angel