Components that you regret parting with?

Just wondering if any of you have had a component that you sold/traded or that stopped working? For whatever reason, you no longer have it and wish you still did? Could you give the component, the reason you no longer have it, and what you liked about it. If you care to comment. I have had several components that for financial reasons or the upgrade bug, that I have parted with and wish I had not later on. Due to the rare nature of some of them I have not been able to purchase them again. It dose not have to be expensive or rare, just an item that has a special place in your heart for whatever reason, that you now regret parting with. If you were able to purchase it again, that would be great to know that as well.

Pete