I've had 2 - been a few years ago and both regarding domain names.
1. The NFL sent me one about the domain quarterbackclub.com They wanted the domain. I still own it
2. Retail shop Montogmery Ward wanted montgomerywards.com from me.(this was back before cybersquatting was ruled on).
Had a decently pleasant conversation with their lawyers - then they too got nasty with me so I redirected the domain to J.C. Penny's - they didn't like that either so I told them to take a nicer tone with me to avoid future embarrassments.
They wound up buying the domain from me.