Changing my original post, a bit.

What would you choose for each category, from current, attainable-in-Hawaii firearms?

Handgun can be a revolver or semi, semi-auto carbine/rifle includes bullpups but can only be 5.56, and shotty can be a 12 or 20 ga pump, O/U, or semi.

Feel free to provide justification (or don't).

For me:

Handgun: Glock 19 (Alt 1: Archeon Type B, but they delayed release, again!).
Semi-auto carbine/rifle: SCAR 16 (Alt 1: X95)
Shotgun: 18.5" Mossberg 590A1 (would love a Benelli M4)

Handgun: Glock 17 with X300 (Alt: Walther PPQ)
The handgun I have most experience with.  Simple operation and can easily teach a new shooter to be (somewhat) proficient quickly.  9 mm is readily available and not that expensive.  Lots of aftermarket support for Glock as well as stuff like holsters, mag pouches, etc. 

Carbine/Rifle: AR with red dot, BUIS, light, and sling
The long gun I have most experience with.  Mild recoiling and easy to control.  Can easily teach new shooter to be (somewhat) proficient quickly.  5.56 is readily available and not that expensive.  Firearm and ammo not all on lighter side given other comparable choices, like 7.62x39.  Easy to mod, repair, etc.  Easy to maintain and keep shooting with minimal effort.  Wide range of uses, from defense to some hunting.

Shotgun: Some sort of Benelli semi-auto (I'd have to buy one first though. . .  )
Proven reliability of Benelli shotguns.  Not personally a fan of shotguns in general, but mostly because I haven't had that much experience with them.

Wild Card (since Stang went there): Semi-auto .308. 
Can be used for hunting larger animals as well as deter the two-legged variety.   .308 ammo is readily available.  Semi-auto as opposed to a bolt action in applications other than hunting.  I currently only have a bolt action .308, but that would be my next best choice for the wild card. 

handgun:  Ruger GP100 Wiley Clapp 3" barrel
justification:  I like Ruger revolvers. you cant beat a revolver for reliability 357/38 is a versatile caliber.  good for self defense or small to medium game, although the 3" barrel would not be legal in Hawaii to hunt.  the WC edition is made to carry: smooth edges, matte blued finish, brass bead front sight, novak rear sight

Rifle:  AR15 5.56
justification:  5.56/.223 ammo is plentiful, and cheap, parts are plentiful.  easy to work on, easy to modify.  lightweight rifle , lightweight ammo.  great defensive rifle, very reliable

Shotgun:  I don't own a shotgun and don't really have 1st hand knowledge of shotguns, so i'll add another rifle:  bolt action in .308 or .300WM
justification:  either caliber is capable of taking any game in Hawaii.  bolt action is great for longer range shooting, very reliable.  308 ammo is relatively cheap and plentiful

handgun:  Ruger GP100 Wiley Clapp 3" barrel
justification:  I like Ruger revolvers. you cant beat a revolver for reliability 357/38 is a versatile caliber.  good for self defense or small to medium game, although the 3" barrel would not be legal in Hawaii to hunt.  the WC edition is made to carry: smooth edges, matte blued finish, brass bead front sight, novak rear sight

Rifle:  AR15 5.56
justification:  5.56/.223 ammo is plentiful, and cheap, parts are plentiful.  easy to work on, easy to modify.  lightweight rifle , lightweight ammo.  great defensive rifle, very reliable

Shotgun:  I don't own a shotgun and don't really have 1st hand knowledge of shotguns, so i'll add another rifle:  bolt action in .308 or .300WM
justification:  either caliber is capable of taking any game in Hawaii.  bolt action is great for longer range shooting, very reliable.  308 ammo is relatively cheap and plentiful

You "cheat" on the shotgun one.  Haha.  I'm just  because I didn't think of that. 

You "cheat" on the shotgun one.  Haha.  I'm just  because I didn't think of that. 

 "if you ain't cheating, you ain't trying."   

"if you ain't cheating, you ain't trying."   

Can't fault anyone for not cheating in a gun fight, or any fight! Come over to the semi-auto hangun world.  Ruger American Pistol or Security-9!!! 

But I'd be ok with having my S&W 686 Plus on me with some .357 Mag hollow points or LSWC, or even .38 SPL hollow points.  Carry it in a leather holster, almost like Rick in TWD.  Except without all the terrible over acting. . . 

Can't fault anyone for not cheating in a gun fight, or any fight! Come over to the semi-auto hangun world.  Ruger American Pistol or Security-9!!! 

But I'd be ok with having my S&W 686 Plus on me with some .357 Mag hollow points or LSWC, or even .38 SPL hollow points.  Carry it in a leather holster, almost like Rick in TWD.  Except without all the terrible over acting. . . 

I have a American pistol in 45.  its great.....for a semiauto.   
I have the old school Security Six. 

little joke I just made up: 
what did the Security Six say to the Security 9?
"who's your daddy?"   

That’s my go to 👀 nothing says “leave me alone “ like that guy does

For a SHTF scenario: BCM Mid 16 Mod 2:

OOOOOO00000000oooooooo !
Digital round count magazine.   
I want one !