And by gun, I mean anything that a character picks up that fires a solid projectile towards a target. No animation, please.
I’ve got one in mind, from a single-worded movie, and it was actually tested on “Mythbusters”. I mention it if no one else does first…but that’s not very likely.
Something like this?
I don’t know if it’s a trick, but I get fed up when one man has a rifle and the other a handgun at a considerable range … and the gunman manages to shoot the rifleman.
Who knows what evil lurks in the hearts of men?
I think Johnny Ringo’s twirling tricks (starting at about 2:40) are pretty stupid. They look flashy but serve no purpose and you risk fumbling your gun and getting shot.
I remember back in the, what, early 90s when Terminator 2 came out and everyone with a (toy) lever action shotgun tried to reload it like Arnold.
And while looking for that gif, I see John Wayne did it first.
I can’t tell on Arnold’s gun, but it does appear John Wayne’s is meant for that. The lever is much larger and appears designed for doing just that. I don’t know enough, however, to know if that was for the movie or if some guns were made that way. I imagine if would be helpful (or necessary) if you only had one hand to use.
The Terminator’s weapon in that spin-cocking move is a shortened Winchester Model 1887 shotgun with a loop lever.
John Wayne’s character’s (from Rio Bravo, I believe) is a Winchester Model 1892 Saddle Carbine with a similar loop lever.
And yes, AFAIK, the enlarged loop in the action lever is intended for spin-cocking. Kind of a specialist trick; perhaps useful for one-handed use, but that would be terrible for accuracy.
All that, and no mention of The Rifleman?
Shame! 
That was also a Winchester Model 1892.
The 1892 is the canonical “old west” lever action rifle.
“This is for fighting, this is for fun.”
Not really a trick, but if you can tolerate Plan Nine From Outer Space one more time, pay attention to the policeman handling the case and his misuse of his pistol. If you can catch the Rifftrax version, they’ll tell you, hilariously, when it happens.
That John Wayne clip is from Stagecoach (1939). It occurs about 40 seconds in on this clip.
“One thing’s for sure: Inspector Clay’s been murdered. And somebody’s responsible!”
I immediately thought of this. He makes every gesture with his pistol (and it looks like he has his finger on the trigger!). He uses it to raise the brim of his hat, scratches his temple with it, gestures towards others’ chests and faces… geez!
Curving the bullet around an obstacle? I forget the movie.
I read once that one man opened fire with his handgun vs another dude with a Winchester at end of street range- the cowboy jury called it suicide. 
Silencers that make a feeble pop sound.
The physics won’t work like that.
Mythbusters did a segment on silencers aka suppressors.
They will reduce the sound about 30db IIRC.
There is a YouTube about that, apparently there are a couple of custom build guns using special ammo which only make a noise that most would not think was a gun shot, and pretty low decibels. Otherwise you need a silencer/supressor and subsonic ammo, and that is still fairly loud- but not gun blast loud.
That would be Wanted.
