As Obama has (thankfully) discovered, it would be pretty hard, if not impossible, to actually do much of anything of consequence fighting against one party or the other in Congress.
Ass-uming you mean, "what would I do if I could do anything", that's pretty easy, really. Start turning back the clock and get us back to the Constitution.
Phase out Social Security/Medicare, cut taxes for everyone except U.S. companies that export jobs, end the Federal Reserve, return us to the "gold standard", stop borrowing, stop spending, start drilling, secure the border while making the LEGAL immigration system slightly less assinine, end the TSA and replace them with competant civilian entities, repeal the health care nightmare and start looking at fixing what's actually broken (TORT reform anyone?), demand every bank and corporation that got a bail out immediately begin repayment with interest which would then be credited back to the taxpayers, followed by getting the govt. out of private business affairs... not to mention education and agriculture, withdraw from the U.N., repeal NAFTA...
That would be a start, anyways.