Is there yet a semi-agreed upon best practice for an icon symbolizing "You are about to tap/click on an icon to open a menu"? Ideally, you really should not go with nameless icons for menu navigation. However, in the limited space of mobile web design, there is sometimes no choice but to use a single icon. Using the word "Menu" isn't always ideal either because of the space and limiting yourself to English speakers.
I've started to see the triple bars being used more and more.
Like in these two examples, the Facebook for iOS app and the Gustavus Adolphus website. Tapping this icon in both examples will reveal a menu for the app or site. Honestly, I don't think the triple bars are a sure-fire way to denote a menu, but it is the most common symbol I've been seeing.
So, does anyone use anything other than the triple bars for a menu icon? I feel like there should be a better way to do this.