Minimum purchase amounts.  I hate them.  They piss me off.  So much so that any business that has a minimum purchase amount in order to use a credit card, or a fee for paying by credit, is instantly a company that I will never purchase anything from again. 

Why you ask? Why don't I just carry cash? Why do I hate small business so much that I would refuse to purchase things from them? Quick Rant 33 explains my dickish opinion on this one, and my anger is directed at more than the just the business owner who charges these fees, I also have some vitriol for congress and the big national banks.