Here the first idea: shorting the VIX (volatility index).
As you can see in the graph below, the VIX has been trading at extreme low levels for the past 5 and 10 years. A surge in volatility could easily pump up the value of the VIX and provide with some short-term gains.
An ETF you can buy that shorts the volatility index by 2x is:
ProShares Ultra VIX Short-Term Futures ETF
Beware of the high costs of holding this ETF.