Personally I'm a fan of the $50 bill. Why? because it just looks good. Whenever I cash a large check I ask for $100 and $50.
You know that several universities use half dollars in their concessions stands - at football and basketball games I go around asking all the cashiers if they have any older halves. I guess they do it as an economic impact statement, then the people spend them or take them to the bank.
I have not found any Halves from my University. But I'll be getting some Halves from the bank later this week.