Bitcoin Forum

Is it possible to send a transaction that will not confirm, but go back to your wallet quickly?

Each client handles transactions that won't confirm differently.  Bitcoin-Qt/bitcoind will continue to re-broadcast the transaction (sporadically, perhaps twice an hour) indefinitely.

Blockchain.info will restore the funds for a transaction that doesn't confirm after about a day.

Each of the other clients may have their own approach.

The behavior of your local client as far as letting you re-spend the funds is immaterial however if the original transaction is still hanging around in the memory pool of miners.   They might hold onto it for a full day or so even perhaps.

Is there any legitimate use for doing this?

It depends on what you mean when you say "to send".

You can broadcast a transaction that doesn't satisfy the requirements of the protocol and all the peers you've connected to will refuse to relay it and will not add it to their memory pool.  Then you can stop broadcasting the invalid transactions, and I suppose you could technically say it "returned to your wallet quickly" since the inputs are still unspent and there are no transactions on the network that are attempting to spend them.

If you broadcast something that any peer accepts as valid, adds to its memory pool, and relays, then there is no way to "get it back quickly".  You can stop broadcasting it, but the transaction still exists out on the network waiting for a miner to add it to a block.  If it isn't added to a block, and if you stop broadcasting it, then it will eventually drop out of the memory pool of the peers that heard about it, but there isn't a way for you to get the peers to drop the transaction faster.

I suppose this conversation wouldn't be complete without mention of the "replace by fee" patch, which essentially allows double spending of an unconfirmed transaction.   While the replace by fee patch is real and exists today, there are few (if any) miners using it so the chances of successfully double spending to recover the funds for your own unconfirmed transaction are very low.

Initial replace-by-fee implementation is now available on testnet
 - http://bitcointalk.org/index.php?topic=199947.0

I had a 0 fee transaction that wouldn't confirm so I tried to double spend it using the blockchain.info tool. But it didn't work and the original no fee transaction confirmed instead! So double spending is harder than it looks.