I have to say Litecoin. I am not saying this from investment point of view though. I have written a lot about Litecoin recently, I am extremely fascinated with the prospect of the Lightning Network, the potential for Atomic Swaps and I am very interested to see how an older crypto like LTC can adapt. For me Litecoin is an experiment that we should all watch to glimpse into the future of crypto.

But....like I said, this is not my favorite crypto as an investment!
As far as investments go Ethereum is proving to be very formidable.