You're referring to RCR123 (16340). Lithium Ion batteries are very useful, but you owe it to yourself to read up on the dangers of using them.
Using Li-ion cells in LED flashlights safely
If you stick with quality protected cells like AW, Eagletac, Fenix, etc. and a quality charger like Pila, Xtar, etc., then the dangers will be minimal. However, I still never leave the batteries unattended while charging.