Right off the bat, I love the idea of the smoking guns. Also, his proportions look amazing. As far as drawing (not colouring, drawing) Yosemite Sam goes, you've stylised him well.
And now this brings me to the meat of the piece, the reason why I've docked a number of stars: shading.
You seem to have gotten a hang of hard and soft shading, but it still feels flat. It still feels like it lacks contrast. If I didn't know better, his hat would have looked like a massive egg sitting on his head. Those guns are chrome, man -- and they NEED hard contrast. Especially if you're intending them to be shiny. You see some really well-defined dark and light places on metal surfaces, so why aren't they here?
I mean, I talk about the guns and the bullets and things but the lack of contrast goes onto his clothes as well. I couldn't even tell that his shirt and trousers had creases until I zoomed in. For something to pop, it must be visible from a distance as well. Had I not zoomed in, I'd have thought his entire body was made out of porcelain.