Mercatox Varies per coin Free Varies per coin Trade fee is 0.25%. While the UI can seem a bit dodgy, Mercatox often lists altcoins not found on the bigger exchanges. Reasonable exchange.

COSS.io Free Free Varies per coin Very high withdrawal fees, however often has altcoins not found on the other major exchanges. As a result can bag some good deals. However, can be difficult to withdraw coins from. Be wary when using.