If you're working on an ICO project, then the best domain to use would be ".io". Why .io? Well, as you probably already know, .io stands for input/output, especially when talking about something related to the tech scene. It is the perfect domain for a company striving to incorporate technological development and innovation into their projects or simply, a startup company.
So to put it together, if your project has something to do with technology, say, Blockchain, then this is the best domain for you to use. Unless, of course, if it is different.
hmm jes .io is nice and has become a standard, i still use .com though, and .io is more xpensive than com its 5 usd per month