I can think about some things that are always annoying: Wait for a person that always arrives late to meetings; that my computer comes up to an error before saving the job I've been working on for a long period of time; spam emails.
Even though, there's one very worse than those mentioned and it's an outdated website. Let's say I get a flyer of a company with a product or service that I interest. The first thing I do is write down the website and throw out the flyer (why put away more papers?), when I go to the site to know more about the company, just there start the problems.