There are some guys that actually want to do more than run their mouths like KG does. There are the crazy, loose cannon types like Nate Robinson and Artest. There are guys like Zaza who made KG run away and punched his own teammate, Josh Smith, in practice. There were guys like Matt Harpring and Vitaly Potapenko.
I don't think Gilbert's gun makes him tough. But there are some guys who have more bark than bite, and as much as I love him, I would have to include KG in that category.
I guess it's all in your definition of "bite". For an NBA player, I've always taken "bite" to mean what they did on the court, even and especially with regards to backing up trash talk. But let's take a look at what KG has historically done in retaliation vs what a "tough" guy might have done in scrapes.
1) Anthony Peeler elbowed KG in the neck during Game 6 of the 2004 WCSF. Garnett took a step towards Peeler then stopped, doing nothing but looking at him.
A real "tough guy" like Artest probably levels Peeler, and misses game 7. An "all bark" guy like KG did nothing but look at the moment, then comes out and explodes all over Peeler's teammates with one of the greatest game 7s in NBA history to carry his team to the next round. Peeler got to watch from home.
Who won the fight?
2) KG gets into it with Antonio McDyess while defending a teammate in 2007. When McDyess attempts to escalate it to a real fight, Garnett doesn't oblige.
But coincidentally, every time Garnett faced McDyess for the entire next year he somehow ended up having huge games...you may remember a few of them, since those games were in KG's first year with the Celtics. For some strange reason, Garnett averaged 24 points and 8.3 free throws drawn against the Pistons that year...seems a tad aggressive for a guy that averaged "only" 18.6 points and 4.6 FTA against every other team that didn't have McDyess as their primary defender on him.
I wonder if there was a connection?
3) One of your listed "tough guys", Zaza Pachulia talks mad trash and headbuts KG in a playoff game. KG doesn't retaliate on the spot. A tough guy like Stephen Jackson may have shot ZaZa for such a transgression.
Instead, KG plays a great series and ensures that ZaZa watches the rest of the playoffs from home. Oh yeah, and as a parting shot KG gives ZaZa a relatively legal hard moving screen under the chin that flattened Zaza. KG got the foul, then moved on to the next round and eventually a title. Zaza (and everyone watching) got KG's message very explicitly. And maybe my mind is blanking, but I don't remember Zaza ever barking or trying another intimidation stunt against the Celtics again...ever.
Bottom line: you can have your NBA tough guys that back up their bark with their fists. Me? Give me a basketball player that's smart enough to retaliate where it hurts...on the scoreboard, with any extra given in ways that don't cost his team games. :Shrugs: I guess, to each his own.