Is there a hold-your-gun-in-the-air emote?
Don't think so. None of the emotes really rely on having a weapon - few exceptions for batsmash and batsmash react, but can't think of any others at the moment.
Orc&Pie No.53230 There is an orc, and somehow, he got a pie. And you are hungry.
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Negaduck: I see you found the crumb. I knew you'd never notice the huge flag.
Is there a hold-your-gun-in-the-air emote?

Kinda like Ron Perlman is doing here:
Slung over the shoulder would work, too. Just anything besides running around like a dope with two hands on it when you're just standing there.
And yes, I've checked all the emote lists, but it could be a cryptic name without "gun" or "rifle" or "weapon" in it, and also the lists can be outdated.
"Hey! You knocked generic cola all over your precious D20 books!"
ED: Now I know how Nancy Kerrigan felt: "Why...?!? Why...?!?"