Conair Custom Cut 18 Piece Haircut Clipper Kit

Q: Can I shave my balls with this?

Instead of shaving, I would suggest waxing them instead. I'm sure all of your exes would agree :D

Q: i need to use this to cut my kid's hair, is it safe ?

Definitely. Turn it on away from kid to begin with and let them come up and hear it. Depending on age and noise fright the kids might be afraid of the noise. Or put in those cheap noise ear sponges. Will not cut the skin or ear, etc. Perfectly great for kids.

Q: If I use it under my armpits would I get knicked? Or is it gentle

You can use it under your armpits, just like after you cut your hair you use it to shave the baby hair or shape the back of your head. Its okay. I use it for everything. You have to be gentle with any machine you use.