First off, how do I disable the transaction fee for low priority transactions? It forces a transaction fee even though I set it to 0.
Use raw transactions. Or modify the source code and re-compile it. (It may also be possible with the new "Coin Control" feature, I'm not sure, I haven't tried that yet).
And what's the easiest way to spend an output twice? (Yes, I'm fully aware of the fact only one of the transactions will make it into the blockchain and be valid.)
Create a transaction that is very unlikely to be relayed or confirmed. Then use pywallet to remove that transaction from your wallet. Wait a few days for all peers to drop the transaction from their memory. Create a new transaction that uses the same inputs (use "Coin Control" or raw transactions).
