Here in Brazil voting is mandatory, but indeed, you can vote for no one. In fact, there are two ways to do so, interestingly enough: you can cast a "blank vote", literally just not picking anyone, or a "null vote", where you input a candidate that doesn't actually exist.

In my view that's the ideal setup. Turnouts is always very high, even though the fine for not voting is laughably small (3.51 reais, literally less than a dollar). Good example of the power of defaults.