1. It's difficult to answer this one, as I have several. If I had to choose one, it would probably be Kuffy.com as I use that as a sobriquet on several fora.
2. Again, I have a couple of hundred for this category, but I guess I should choose LimoCat.com, as that was going to be my example for the quick flipping of a name found on Expired Domains, but I haven't devoted any time to selling it.
3.I think I will select OilDrum.com for this one. It may not be my most valuable, but I have a certain affection for it.