Vimes's refusal to celebrate after killing Angua's brother, because 'that would make it murder'.
The mere fact that he pulled off this, given that the victim was a werewolf, further highlights Vimes' badassitude.
Hey, he manages to kill two werewolves with his bare hands, in quick succession, after going over a bloody waterfall. That. Is. Badass.
...and not just a waterfall, but having been forced to flee from the werewolves, naked and unarmed, through a wintry forest as part of the werewolves' twisted "game." A game that is, by all means, impossible for the hunted to win, but Vimes does anyway. Though given this is Sam Vimes we're talking about, it was probably necessary to even the odds for the werewolves.
Detritus's refusal to just follow orders. Is it any wonder why Vimes calls him "One of his finest officers"?
I also give one to Vimes for training his subordinates to be the kind of “men” that he knows would disobey even him if they thought the order was wrong. And being proud enough and confident enough of that fact that he orders Detritus, who used to take things so literally he'd knock himself out saluting, to kill someone, knowing he won't. That's trust.
The guard in question ceasing to be so obedient shortly afterward, and Vimes letting him by. "The man's decided he's got a duty to do."
When Sam, Sybil, and others are facing down a mob of angry dwarves, Sybil wins them over to their side by singing an aria from a famous dwarvish opera, thus helping the group juggernaut their way into the palace.
Sybil reduces a squad of dwarves guarding the doors to tears, forces Dee to let them in to the Low King, and negotiates a very advantageous trade agreement. Because she'd sung in an abbreviated version of an opera and got bored sitting around the embassy.
Sybil kills a werewolf. Well I assume she killed it anyway, since she whacked it with a steel bar hard enough to bend the bar.
While apologizing for whacking it with a steel bar. The woman is a Lady.
It's highly doubtful the werewolf is dead. (Only fire or silver, remember?) But none the less, insanely badass. CARROT couldn't knock out a wolf. (And Vimes fought tooth and nail to knock out/defeat his four or so.)
There's the moment described in Made of Plasticine where the odd-looking and seemingly weak "clerk" Inigo Skimmer attacks some enemies by chopping them in the neck with his hand. Rather than stunning them as might be expected, it takes their heads clean off. Granted, it's because he had a (ridiculously sharp) palm dagger, but still.
Inigo's moment was even more impressive than that. More than a dozen men attacked their carriages. Vimes killed one. Inigo killed six. When Vimes asked him ironically why he didn't kill more?
Inigo: I only have two hands...
Vimes's prediction that by the time they get to Bonk, the six dead men will have multiplied via the rumor mill into thirty and a dog. He was accurate down to the dog.
Just about any of Vimes' fights in this book — the one in the tree was especially good, especially when you realize that Vimes is beating up werewolves, bare handed.
Gavin attacks Wolfgang, despite knowing that the bastard has just beaten a guy who can floor trolls.
"This is how you win a dogfight!" - Gaspode the Wonder Dog, living up to his name
"Inigo looked down and swallowed. Vimes had a knife, too."
Inigo: Then it's true. You really are no gentleman."
So commander Vimes is away. Captain Carrot is away as well. The current acting officer is Fred Colon (and the rest of the Watch is on strike because of that). Ankh-Morpork is having a completely crime-free day, because every criminal knows that Vimes is going to be back, very unhappy, and with a very big shovel.
This exchange regarding The Piecemaker:
Vimes: Detritus, you can't fire that off in here! This is an enclosed building!
Detritus: Only till I pull dis trigger, sir.
Even better since, at this point in his character development, it's equally possible that Detritus is being literal or letting off a one-liner, and you really can't tell which.
Vimes' stroke of genius that keeps Tantony from arresting him on the grounds of the embassy.
Vimes: Igor, I want you to tell this young man where he is.
Igor: He's in Ankh-Morpork, marthter.
He then uses this again as grounds to arrest Wolfgang, along with baiting his opponent into explicitly saying he's resisting arrest to justify his use of force.