Volatility (along with RTP and Hit frequency) is a crucial parameter of any slot game. It affects gaming experience in a big way (learn more about volatility and its types), so everybody should establish it before trying out a new slot.
However, have you known that some video slots let us, players, change the volatility level basically on the fly? The slots, which allow to do so, are called Adjustable volatility slots. Though it is fair to say that the Adjustable volatility feature is not too widespread in the industry (yet?), and there are not too many products on the market with custom volatility level.
Look at different volatility type slots: