I'v only seen one straight flush which I had to pay out for lol. I raised preflop with Aces(As,Ad), some guy called, flop came 2,3,4s. I bet, he called and I assumed he had maybe A,Ks or some high flush draw. Turn, 5s. I smile, totally sure someone wouldn't call a 5BB bet with some crap suited connectors and maybe made K flush or so. I bet half the pot, he went all in. I was 100% sure I had this straight flush. He turns over 6s,7s.
I was nearly sick.
Never seen a royal flush yet though..