I have always preferred developing web applications that are simple. So many times a project gets blown out in scope and gets way too complicated.
I remember specifying a site one time that I gave a 40K bid for. Got the project....then 6 months later through scope creep it was done and the budget was 250K. Then 6 months after launch it was abandoned because it was to complex to use.
So I am always advocating a simple tool or web application
that is easy for users to understand and use.
Looks like there are other like minded individuals, here is a web application I found that showcases other "Single Function" web sites and applications.
It is appropriately called Single Function