ETH and IOTA. IOTA may be one of the top altcoins and is modeled after the Internet of things (IoT). It has come a long way in its price as well. Ethereum is amazing because it introduced their own Ethereum network, in which other people can create tokens based on it. It made it easier for developers to create their own tokens, because they dont need to create an entire blockchain from scratch.
To these two you can add Ripple. Now, however, its price falls. But, I'm sure it's temporary thing. Well see how this technologically improved currency will rise again. Some talks that Ripple will beat Bitcoin with the time.