Disclaimer: I don't own Star Wars or The Clone Wars.
Spoilers: For Episode 16 "The Hidden Enemy"
Chopper
His squad mates know about the necklace now, so Chopper doesn't bother to hide it anymore. Sometimes he even wears the thing around his throat, and he doesn't care who sees it.
He keeps making them, too. Sometimes he uses fingers, sometimes the triggers from droid blasters. When the squad takes the field, he brings some of the necklaces with him, and he makes sure the clankers see them. He wants the severed fingers of their comrades to be the last thing those bastards ever see.
Chopper knows the Jedi rationalize their part in the war by saying that the droids aren't really alive, and so they're not killing anyone. He thinks it's a useless rationalization, though, and he doesn't entirely understand it. They're at war, and war means killing. He doesn't see the point in denying that.
And he knows that the droids are just as alive as he and his brothers. That's why he takes the fingers. Because they're just like him.