There are many out there, but most of them has 0 to no volume at all.

Personally I've got my eyes on Stakenet's DEX solution, which will run on masternodes. It's a lightning DEX, so it's gonna run extremely fast in comparison to any other out there, and since it's run on masternodes, which are required to hold the chains, you wont even notice the difference between the Stakenet DEX, and any other centralized exchange, which is crucial for adoption and user friendliness.
Problem is, if you want to exchange BTC for LTC, you need to download both chains (And they are massive at this point) to even be able to trade.

Problem is the liquidity, it always is. Stakenet is adding a DEX Aggregator, which will combine multiple DEX orderbooks into their own adding tons of liquidity, and ease of use.

This is a based answer, since I'm invested in the project itself, but it's 100% my best recommendation at this point. I believe the DEX will be launched within a couple of months at most.