Glade Riven
Adventurer
Let's find out...Do you mean that most of those are supported by D&D gun mechanics?
Otherwise that's just a list of more ways in which the mechanics don't support what some people may expect.
Abnormal Ammo? Check. (Pathfinder, Iron Kingdoms, even certain d20 Modern Suppliments)
Accidental Aiming Skills? Check (can happen d20 crits on anything with 2 HD or less)
AKA-47? Check (Iron Kingdoms)
Ammunition Backpack? Check (you can put ammo in your backpack - or even a bag of holding.
A-Team Firing? Check (play experiance, poor rolls leading to lots of misses)
Almost Lethal Weapons? Check (Hit Points; mooks with low HP to start die fast and quick, PCs survive a few flesh wounds)
Anti-Air? Any range weapon counts
Armed Altruism? Look, if the players want to give their weapons away...
Armor Piercing? Check (d20 Modern, Iron Kingdoms)
Skipping forward to some more applicable...
Bizzare and Improbable Ballistics? Roll a d20
BOOM! Headshot? Oh, look, you crited.
Bullet Catch? I think there's a monk feat for that.
Bullet Dodges You? Someone failed their d20 roll
Bullet Proof Vest? Huh, I wonder what AC is for...
Bullets do not work that way? Neither does any other weapon in this game, so why are guns special?
I could keep going on and on, but in a d20/D&D campaign I played in, almost every one of these tropes came into play for one reason or another. In some cases, the rolls determined that a trope needed to be played off of to explain what happened - like in the second session of the game where my elf paladin kicked open a door and the 8 or so orcs with shotguns and readied actions fired...and missed.
But we've gone off into a rather absured tangent from my original post, which is not helping. Or maybe it does, since it shows that us nerds will still spend time arguing about the nature of guns in the system whether or not they are ad-hoc magical in nature or not.