Fibonacci gives +8 mult per scored Ace, 2, 3, 5, and 8
Supernova, Ride the Bus, Green Joker, Fortune Teller, Flash Joker, Spare Trousers, and Erosion scale by positive divisors of 8 so they can give +8 mult too
Ceremonial Dagger Swashbuckler, and Raised Fist can sometimes give +8 mult depending on the context
Misprint has a roughly 4% chance to give +8 mult for each time it triggers
Jolly Joker gives +8 mult always for every time you play a Pair
In the 4th round you have Popcorn, it will give +8 mult