Not to forget the client that wants his website for free, but promises to tell all of his friends that you made it. Then everyone will want you to make a website and you will be rich in no time. In fact - for offering you this great opportunity you should be paying him to let you make your website.
Or the client that wants you to ad little feature to his website. Should be no problem at all to implement, five minutes works to the max. All you would have to do ist add a little button there on the left side of the navigation bar. When he just asked you to implement a feature in the website that would be like asking the car mechanic to add a 4 Wheel Drive to your car. I am sure the mechanics biggest problem is where to put the button to activate it.
Reminds me of this: