[Oni]

What is your favorite firearm?

Whether it was in Counter-Strike, real life, or from a movie.... Guns are everywhere.

For me, it is the Heckler & Koch 416. Supreme German engineering, made to be submerged in water. The HK416 was used by Tier 1s during the GWOT and also the rifle that shot Bin Laden.
A close second would be the MK18, which was an evolution of the military's M4 program utilizing Daniel Defense's RIS II rails. Both rifles have seen heavy use by operators and law enforcement.