I like to use the watch video section on an idle desktop at work. Doesn't cost anything and it's a free altcoin every few weeks.

It's actually pretty decent if you think in terms that they're giving you a free altcoin you wish to hold longterm for basically doing nothing. I wouldn't recommend it for anything above 5 USD. A few months ago it was good for coins like ARK, Sia, XRP, DGB, and ADA; still is for a few of those.