At our table, sometimes it happens that the DM says, e.g., "everyone, roll a fortitude save", then looks in the book or somewhere studying the DC or effects. Meanwhile, players roll. If the roll is OK, players yell the number. If the roll sucks, a player might grab the die again, wait for the DM to look up from his notes, and then throw again, in front of his eyes. This is kind of tolerated.
Also, I have a wooden 6sided die and I have hammered a piece of a metal nail into the number one. But it ain't really working