As for coins, I would gladly use coins in $1, $5, $10, and $20 increments. I would also appreciate $500 and $1000 bill denominations.
It was a lot easier to pay for small items when ice-cream cones, soda, candy bars, hot dogs, etc. could all be paid for with a single coin. And returning to 10 cent sodas isn't ever going to happen.
I really wish the Pepsi machine at work accepted $2 bills :^(