Acupuncture
The delightful website Science-Based Medicine recently summed up a plethora of studies on this scam, and found that as a whole they establish clearer evidence of its untruth than any one of them could.
For example, acupuncturists noted that real medical studies hypothesize a mechanism for why a treatment might work, then perform tests to see first, if the effect occurs and second, if the effect and the therapeutic benefit are correlated. Acupuncturists perform a quick sleight-of-hand with this sequence: first they measure what happens in skin when needles (with or without electric current) are stuck into skin, then they propose that the mechanism for acupuncture's effect is whatever they measured in step 1, and then they correlate that with the therapeutic benefit. It's pretty subtle, and lay people will mostly not notice the switcheroo, but it's absolute crap as far as science is concerned. You don't get to observe what happened and then, ex post facto, say that it's what your theory predicted!
Another damning bit of evidence against any reality to the claims of acupuncture is a meta-study that found that acupuncturists' training... or lack thereof, their adherence to the exact points of insertion... or lack thereof, in fact, whether they inserted needles... or merely poked the surface of the skin with toothpicks. In fact, none of these correlated with improvements in symptoms. What did correlate with improvement?
A nice person being concerned about your symptoms and attending to them.
I suppose this means, being a nice person and being attentive to the issues people bring to you is all the qualification required to be an acupuncturist. Now that I think about it, I wouldn't mind "being nice and attentive" being requirements for a number of other occupations. But none of those things should qualify for a plugged nickel of healthcare money, and sadly, acupuncture does.