The main scams and dubious devices in the world of hair removal are:
“Transdermal electrolysis” (aka “transcutaneous hair removal“)
“Hair growth inhibitors” and other over-the-counter topical products
Overpromise (sales pitches that exaggerate results). This includes almost anything sold on television.
Here’s a longer list of dubious achievement all-stars
Sadly, there are too many scams to list them all here. If you aren’t sure if a product or device is legitimate, visit my hair removal forum.