If I have a few mins to kill during the day (usually when waiting for ETH/BTC to hit the exchanges from my wallet) Ill sign up for an airdrop or two. Most of the ones that I have either haven't hit exchanges or are worth under $1.
TRON (TRX) was the first one for me that actually did something.
500 free TRX peaked at ~$30 and is currently worth ~$19
HODLing!
Do you remember REBELLIOUS Airdrop, which was provided as 4500 REBL to everyone who participated, which at peak reached over an ETH and that time ETH value was ~ $1200, nothing better than that.
Next to it is Ontology (ONT)