...or any text you often need to write in form fields.
Works with inputs, textareas and contenteditable elements.
Doesn't work on HTTPS on Firefox 23+.
javascript:(function(d){d=document.activeElement;if(d.tagName=="INPUT"||d.tagName=="TEXTAREA"||d.contentEditable=="true"){d.value=d.innerHTML="my_email@my_email_provider.com"}})()