I like to legally "launder" my investment money through my credit card too. I've used my card to purchase I-bonds for years and will miss being able to do that -- although the current I-bond rates are miserable. It's hard to find a transaction that is closer to a "free lunch" than being able to make your regular investment transactions using a benefit paying credit card. You are spending your money on yourself in exactly the way you want to, and the credit card company pays you a benefit for it.
I have started asking if I can use my credit card for almost everything. Two months ago, I paid for a new car with my VISA. In the past I would have written a check, but adding the step of charging it on the VISA first and then paying off the VISA bill has big benefits. Of course, I always pay the bill off immediately so I don't pay interest, and the laundered payments win me airline miles for my next trip.
I have one card (AAA VISA) that gives me a 5% discount on any gasoline purchase I make. In addition, it pays you a $50 gift certificate on each $5000 you charge through them. The gift certificate is limited to AAA stores, but last year I needed to upgrade my luggage (which was being held together with duct tape in some cases) and I was able to get what I needed using the benefit certificates. Around here (Phoenix) the cheapest gas by 2 or 3 cents/gallon is usually Arco stations. But they won't take credit cards. I end up saving more than 7 cents per gallon by finding a gas station that offers the convenience of credit card pumps. Since I drive about 50,000 miles per year, this really adds up.