Can I 'un-import' private key? I'm checking out the test net and a friendly person gave me access to his private key so that I didn't need to generate coins, so I importprivkey the key, sent me some coins and...

Well, I understand that now my wallet contains those 2 addresses, how can I remove his address, if possible?

Why do I want to do this? Because I'm testing stuff out and I don't want his transactions / tests cloud mine.

Thanks
There is no way to 'un-import' a private key in the core client. What you could do instead is:


Make a list of all the private keys you do care about.
Close your client.
Move the wallet.dat out of the data directory to some other location.
Start the client.
Re-import all the private keys that you do want in your wallet.


This is sort of a work around, and it may be kind of tedious, sorry there isn't a better solution currently.