A beard trimmer. Shaving sucks and irritates my skin, plus I look like a baby without facial hair. But that's only one benefit.
I have been using a beard trimmer to cut my own hair for the last 10 years which has saved me probably $2000 worth of haircuts (estimating a $25 haircut + tip every 2 months). Not to mention saving about 1 hour waiting at the barber every time. I only messed up once and had to do a buzz cut.