In Bang!, can you use two beers?
Yes, you can use multiple Gatlings or beers in a turn. These cards are not played in front of you, they are played directly into the discard pile. They are also not "BANG!" cards, so you can play more than one a turn (only the card "BANG!" is a "BANG!" card).

You cannot, however, use multiple barrels. You can only have one of each blue (or green) card in front of you at a time.