Litecoin.
Still below $50 per coin. Likely the first alternative cryptocurrency, created in 2011. It's creator, Charlie Lee, just quit his role at Coinbase to focus on further development of Litecoin. Litecoin will have 4x as much coin mined as Bitcoin, therefore a barometer of price potential (should demand be equal) is 1/4 the price of Bitcoin. Today that would be $600...so from that perspective Litecoin has yet to see its day, therefore you haven't missed much.
I completely agree with this. Litecoin has been calm for a long time but something big in terms of price is bound to happen sooner or later. I think it's pretty much undervalued at the moment. A great time to get on board.