Whomever Paul endorses in the Presidential election is likely to be the best option, but if any of them are anti-fed, non-interventionist, and of the Austrian free-trader variety (or maybe even the Chicagoan, but still anti-fed)---i'll support Sanford, Flake, or Johnson.
I think Johnson would cause some problems because he says he's pro-choice (but supported pro-life stuff while in office?) and doesnt seem to be outspoken on the war or the Fed. He's GREAT on the War on Drugs though. He's my top guy.
After that, Sanford. Sanford has proved he's willing to buck the system (releasing pigs on the floor of the SC House to protest "pork", AWESOME!) and is anti-REAL ID. He worked with Paul while in Congress in a great way.
Flake is now against the War in Iraq, the Patriot Act, and is beloved in Arizona and by pork-busters everywhere. Unfortunately he is still somewhat of a hawk, hasnt shown anything on the War on Drugs, and we know nothing about what he thinks of the Fed.