I can create my own font file with icomoon so it only contains the icons that I needed for my site. Only issue I have is that there is no way to save the created font file so that I can modify later.
It's different. Icomoon is brilliant for creating a preset group of icons which will be used in a predictable way. But sometimes, especially during prototyping, you don't know which icons you'll want. Just being able to include a pretty thorough library which renders consistently and gives you a decent level of control is a nice weight off your mind. It would be nice to have a subsetting tool, but imo that's what Icomoon's for.
Btw, you can save fonts in Icomoon - just click on the save icon in the bottom right and it'll save a settings json file which can be reimported.
As far as I know they use the fontforge engine (as it is scriptable from the commandline) to drive icomoon, it is very easy to load the fontfile you created with icomoon into fontforge, load another instance of fontforge with a new fontfile created on icomoon and do copy/paste between them.
Of course you can also load the original fontfiles that icomoon works with and use them into fontforge.
I can create my own font file with icomoon so it only contains the icons that I needed for my site. Only issue I have is that there is no way to save the created font file so that I can modify later.