I just found a neat built-in feature inside MonoDevelop :
Whenever you put the word "TODO" (case sensitive) in a comment, it highlights the word in a flashy color so that you can see it instantly when browsing your code.
Can be very helpful to find an old Todo thing !
Considering it's kind of cool, and totally unnecessary from MonoDevelop devs to implement that, I guess there are other built-in tricks like that.
Do you know some ?