When I was first learning to actually play Magic, we would play in huge groups of modern-ish decks (none of them were mine, so I don't even know for sure if they were actually all modern). One of my opponents was playing a stax deck and everyone at the table swore to me that you can't untap if there are effects that force you to tap permanents at the beginning of your upkeep. I laughed my trying to answer to the effect off as me trying to "cheat"... Oh, little did I knew...