Never earned any free bitcoin. 
Of course you'll never earn "free" bitcoin cuz you've earned and it means you put time and effort on it. Even on faucets, it shouldn't be considered free bitcoins since you are putting an effort solving the captcha and you spend time waiting for the timer to claim again
There are giveaways and BiPolarBob. You can earn some free BTC that are really free.
Of course you should never expect to receive BTC, but earn some bits for free is possible
I think its not totally free since you have to put a small effort to post your BTC address on such giveaway threads like on BipolarBob
haha but its considered free by everyone BipolarBob is such a nice guy, I received free $15 worth of BTC from him before from one of his giveaways 
So the conclusion is there is no free bitcoin in this world, right? even from faucet or giveawy since you have to doing something for get it,then i think the reall things you called as free bitcoin is when someone has sent amount of bitcoin to the wrong address, and the wrong address was your address, like my friend on one of a giveaway