I picked up the first season of Numb3rs for 25 cents at a yard sale. I'd heard of it, and, being a math geek myself, decided to give it a try. I am ever so glad that I did.
Numb3rs is probably the best American TV show that I have ever seen in my life (I say American TV because I tend to watch stuff from BBC more than, say, Fox or CBS). Yes, it makes math look super-cool and (dare I say it?) fun. Yes, the acting is excellent and the stories are up to date (CSM gave a very nice example up above under the 'is it any good?' tab). And yes, it can be quite violent. The first episode seemed to be one of those 'let's make the first episode as violent and disturbing as we possibly can so as to shock the people into watching this show!' type episodes: in one scene, a woman is held hostage in a garage with a plastic bag over her head (she is rescued just before she passes out), and there are lots of images of female corpses that have been beaten, branded with a blowtorch, and raped. But once you get past that first episode, things calm down a bit: the plots center around things like stock fraud and bank robberies and such (please note that I'm referring to season 1 - the other seasons rank a little higher on the 'violence and gore' chart). Parents, if you have a teen who isn't really into math, I'd recommend this series to them (or anyone at all over the age of 14) and I'll bet you a steak dinner that this won't change their minds about math, at least a little bit!