I dont have any that i think are worth loads in terms of money.
I suppose my ukspace4u domains are my most valuable as they are my business names and what makes me my money!
I have a few that may be important / valuable, never had them valued though so i dont know how much they are worth...
hostchat.co.uk
hoststatus.net
my-server.info
registryuk.com
windows-ce.com (won in an ebay auction for £5)
webpurchase.net
securedspace.net
Yourhostsucks.co.uk
domain-control.co.uk
Thats just about alll the good ones i have that I can think of.
One of these days, ill put them on my server and actually create sites for them (as most just go to a holding page, or agccworld.co.uk)
LOL... same here, i've got markcastle.com, .net, .org & .co.uk - a guy in Oz also called Mark Castle, recently mailed me and said, "Strewth, bit greedy with the domains aren't you mate".