So I wasn't paying great attention when I sent over a payment through bitcoin core and left the transaction fee at the "Recommendation" of 0.00001507 BTC/kb. Now it's been sitting 12 hours, without a single confirmation. Is there any way I can take this back and resend it with a normal amount of transaction fee?
There is a way with some technical skill to up the fees of the original transaction, but with a fair amount of risk.
Right now you have basically tied up the TXOs that were used in the transaction that is sitting in the mempool. If you were willing to risk more TXOs, you could spend from the change address of your original transaction but add a whole lot of fees to it. If your real technical you can do this with just your change address. If your not technical you can do a sweep of your whole wallet and burn all your TXOs in the process.
This method is called CPFP (Child Pays for Parent) and currently 4% of the miners support it. That means you bump your odds of getting into the blockchain from effectively 0% right now, to about 4%. If more miners support CPFP this would be common practice. It would also be great if some wallets actually had a non-technical, point and click way to make a CPFP transaction.
So yeah... think your screwed... either wait, or read up on CPFP.