Why not just do a balance transfer to another card?
For my debts, I have a mortgage at 3.7% interest and a TSP loan at 1.75% paid to myself used as a DP for the mortgage. I have no other CC debts, student loans, car loans, etc.
Right now, I am looking into getting BIPV Solar panels (and consequently a new roof) in order to apply for SRECs (~$450/MWh or ~$3k a year on a 6kW system), tax credits (30% of roof/solar cost since it is BIPV), and general electrical/environmental savings as an option for this 2% cash back 0% interest "loan". This process is more than a bit frustrating, but if I can make it work, it would be a great return. It is the best thing I could find or think of at this time besides just taking out a cash advance and putting it into any investment account. I would rather not give away that "free" 2% yield.
I was also trying to find if it was possible to physically buy a royalty (song or yielding patent) with a CC somewhere and try to pay off the CC with the royalty payments, but I can't find a good royalty 'brokerage' that you can just buy things with a CC. If you know of any of those, I am all ears.
This sounds like the more interesting option than traditional investing -- perhaps you could use the CC to purchase other energy efficiency upgrades like insulation, energy efficient appliances, or audit for your home? Or further, what about an in-home battery and Chevy Volt? MMM has some great articles on the subjects.
As a side Note, I used KickFurther mentioned above to help meet some spending requirements for CCs. It wasn't really worth it for an investment return. Over the past ~2 years, I purchased about $3000 in various inventories, and received just $3110 after accounting for charge-offs on the or so offers that failed. So call it just 3.5%, but likely not over a single year. Which is fully taxable. As such, I am no longer invested in the platform.
If you want to get riskier, you could make a large deposit on FanDuel -- for which your CC may lock up and require verification. Are you knowledgeable about fantasy football and do you like to gamble? If you deposit a large chunk of cash, it must be wagered once -- in theory, on the lowest risk to reward type of game. After it's been wagered, the funds have been 'washed' in a sense and are withdraw-able to PayPal or you bank (and fully taxable), and then can be invested in traditional securities.