I constantly hear about inheritance being a prime factor in determining if something is OO or not, and how useful it is for OO programming. Everybook I read that talks about OO eventually mentions inheritance, along with the standard animal or car examples. But I don't think I've ever used inheriting in my life, not that my life is especially long or I've done lots of programming, but I've done a bit and I just never seem to use it.
So my question is, when/what have you actually used inheritance (for) in a 'real' project? Real in this case meaning a project not done solely for experimentation purposes.