Mainly, they use a melee attack or charge, but they occasionally throw a lightning ball that can momentarily stun the Vault Hunter.
The easiest way to take down a Loot Goon is to get behind cover or atop a roof. It will then do a "taunting" animation, whereupon the Vault Hunter can plink away with headshots for an easy kill. Conversely, just backpedal and blast away at its head with a shotgun.
Besides lobbing lightning balls, they occasionally perform an electric slam attack that is similar to Sledge's skill, and does considerable damage to shields.