If someone in a bar in a game setting pulls a weapon, they're probably just having a little fun. Best to laugh and move on, rather than over-react.

Unless they're not having a little fun. In which case over-reacting is the best policy.

Can't decide which? Roll a die. That's what the GM's doing anyway.

Transcript

Obi-Wan: This little one isn't worth the trouble.
Ponda Baba: Aw, thanks, but don't worry, I got this. This tetch is goin' down.
GM: He pulls a gun on Luke.
Obi-Wan: I disarm him. 20.
[SFX]: Whooom!
[SFX]: Whooom!
{Obi-Wan cuts Ponda's arm off}
[SFX]: Splat!
Obi-Wan: <sigh> I guess that was inevitable.
Ponda Baba: What the hell are you doing? I was just messing with the kid! That arm's gonna take me hours to grow back!
Obi-Wan: Uh... I'm sorry... but...
Ponda Baba: Nah, just kidding. It's gone forever.
Ponda Baba: And it hurts a lot.