One of my most memorable airdrop was Hydro Token. This Hydro Project was no-ICO. The large airdrop brought each participant 222,222 HYDRO. Back in the day, when Bitcoin reached all time high, those tokens equaled to approx $3000. I didn't sell them at the highest price tho. When bitcoin dropped a little bit, I sold those tokens at got $2100 in fiat. That was my most lucrative airdrop ever. Nowadays, such airdrop is really rare. Bounty, in general brings more moeny. The effort that bounties required is also higher. But everything has positive and negative aspects. If a project is scam, then your effort will be wasted and you'll feel regret.