Stellar is doing a giveaway at the end of this month, Byteball gives free coins based on how many BTC you have, Bitcore does too and I'm sure there are a few others.
Byteball for example with a 20 BTC balance gives you about 1.24 GB of Byteball per month until the distribution ends. That's currently worth about 0.3 BTC. That's completely free. All you have to do is sign your Bitcoin address. There's no risk.
Stellar - https://www.stellar.org/blog/bitcoin-claim-lumens-2/
Byteball - https://byteball.org/
Just been looking at the stellar giveaway. You have to provide your facebook ID then tell them all your bitcoin addresses. Really what are they up to distributing a new crypto coin or linking bitcoins to people via your facebook ID?