There is one situation where you can lose with a Royal Flush. If you're playing 5-card draw, with the bug, it is possible to have 5 of a kind Aces. This hand would beat the Royal Flush. I've rarely played at any official room where a bug (or wild cards) was in play (only home games), so I've never seen this officially spelled out. But, it's the house rule at any of my family's games.
The only time suits matter is comparing the ranks of individual cards. This is useful when determining who has the button (as mentioned above), or when playing 7-card stud games (since the bring-in is often based on the strength of your door card).
Originally Posted by Jblocher1
Be sure u don't lay down a club royal flush because ur concerned about ur opponent having a spade royal flush... That would be the worst play made in poker history.
Totally off topic:
This makes me think of a Sklansky quote about errors in poker. He was talking about errors and how costly they could be. He asked the reader to imagine a hypothetical player who would just fold any Royal Flush (even when not facing a bet) as soon as they hit it. As errors go, this is always going to be a huge one. But, as mistakes come, it's not going to be nearly as costly as calling too much pre-flop -- simply because you're going to have a lot more opportunities to mess up pre-flop than mess up playing your Royal Flushes.