Yeah,except not instakill and more awesome.
What if your holding an RPG launcher, tau cannon or any really big gun that needs two hands to hold? Where do you put your hands or the gun? I can’t imagine easilly being able to hold the heavy gun with one hand, pull out the crowbar and deal an attack all within a split second. Although to be fair, it’s not much different to quickly pressing q and clicking.
I don’t get it. What do you want to happen?
If you are holding a gun with two hands, you are holding a gun with two hands. If you want to switch to another weapon, the one you are holding gets put away, and you pull out another weapon.
You’re expecting that kind of realism in a game where the main character can carry two handguns, a shotgun, a sub-machine gun, a rocket launcher, a number of grenades, satchel charges and trip mines plus a crossbow, two nuclear powered devices AND an alien creature attached to one hand all at the same time plus the associated munitions?
Short answer: HL1 was this way.
Shortest answer: Yes.
Barney Calhoun greeting Freeman
Obvious troll is obvious.
Bit of a late reply, but yeah, this would be awesome, as you walk towards small stones, they sort of slowly drift into the air, not too far away from you. That would be awesome. 
There’s probably a way to do this through the console though I don’t know how. I’d like that pressing the g button goes straight to the crowbar since the Gravity Gun isn’t in the game. The 1 button is too far up for my liking. Though there might already be a use for that key.
What I meant was, if you are holding a gun and you do this special crowbar attack thing, your two hand will already in use. You can’t just have a third hand come out of nowhere with a crawbar, so this is a problem with that suggestion.
What about Snarks?
Throwable crowbars with satchels taped to them. Er, I probably belong in the Daydream Thread. 
Why would you want to use your crowbar when holding a gun? Just shoot whatever is in front of you with your gun.
bind “use weapon_crowbar; +attack; lastinv”
should do the trick. you may need a wait in there somewhere.
That would be when you take one of your hands off of the gun and deliver a swift crowbar blow of justice and SCIENCE.
Good graphics won’t be in Black Mesa?
:facepalm: “AN ALIEN CREATURE attached to one hand”
Pretty sure he was talking about the Hivehand.
^ This, Snarks aren’t attatched to your hand.
Unless they are biting into your flesh.