AR-15
SKS/AK-47
Pistol cal carbine such as Kel Tec Sub 2000
Glock of some sort
Remington 870 (Mossberg 500 if you prefer that setup)
7.62x51 rifle of some sort
And a good Ruger 10/22 never hurt anyone
It is definitely not a good idea to use any key parts from an airsoft gun to replace on an actual firearm. The only thing I would ever try in this form may be the cheaper Magpul mbus sights. You would definitely mess something up with your gun if you tried this.
I have used my Cold Steel Trailmaster San Mai for years and it is absolutely outstanding. Stays sharp forever and it never fails. It is an expensive knife ,yes, but you definitely get good quality that will last a lifetime. And if not, you got yourself a warranty.
I have The .243 barreled one and it is okay. Had a few problems with it not ejecting and light striking but that also could have been the ammo. They're definitely worth what you pay for though.
I have used both for hog and other animals, and I must say the 22 Magnum is great for closer ranges. Anything too far and you'll need something bigger.