Here are some examples of notable cryptocurrency airdrops and their caps:

1. Ethereum (ETH)$ETH

- No airdrop, but an initial coin offering (ICO) cap of $18 million in 2014.

2. Bitcoin Cash $BCH

(BCH) - No airdrop, but a hard fork from Bitcoin (BTC) in 2017.

3. Stellar (XLM) - Airdrop cap of 16 billion XLM (approx. $16 million USD at the time) in 2017.

4. Cardano (ADA) - Airdrop cap of 26 billion ADA (approx. $63 million USD at the time) in 2017.

5. Ontology (ONT) - Airdrop cap of 10 million ONT (approx. $20 million USD at the time) in 2018.

6. Tron (TRX) - Airdrop cap of 30 billion TRX (approx. $15 million USD at the time) in 2018.

7. Binance Coin $BNB

(BNB) - Airdrop cap of 200 million BNB (approx. $10 million USD at the time) in 2017.

Note that these caps are approximate and based on the value of the cryptocurrency at the time of the airdrop. Airdrops are usually used to distribute tokens to a wide range of participants, often to promote adoption and community building.