ChessClock+

After using this app to play all of my over the board games, I can confirm that this clock is better than all of the others. It is free, and has every imaginable feature. In addition, the creator is very responsive and often implements the suggestions that people give.

Completely customizable and free! What more could you ask for?! One recommendation: The delay is currently shown as just a bar, so you can't see specifically how much time you have left. There should be an option to switch between the bar and the actual number. I'd choose the number! EDIT: Developer implemented this request. I wish I could give 6 stars!

This has all the things that you could ask for. When it says customizable, it means customizable. In terms of functionality, this is by far the best chess timer app I’ve ever used. One app that I know of does better in the visual department, but that’s it. Unless you are doing some very standard games, no other apps will have what you need.