My smoke d10s used to be absolutely lethal. They seemed to try to kill my character for whatever game I was playing. Sometimes I could trick them into thinking I was in fact playing a different game, at which point it they would be extreamly generous until they figured out they had been tricked.
As a GM they had the cool property of trying the players metal right up until the climactic moment at which point they would allow the players to just barely overcome.
When I was a kid (boy was that a long time ago...wow) I used to be pretty good at judging the rolls of d6's and d10's such that it wasn't really rolling as such, but I needed to do it in a box top. I could pretty well depend on high damage or a red feat whatever if I needed it. I can't remember why or when I stopped doing it, probably because it was lame. They would roll, but the outcome wasn't much in doubt.