Rearing. I would tackle a bucker, but never ride a rearer.
With bucking, you just fall off. With rearing, the horse could land on
you. I can ride a buck -- keep the head up and sit back. Rearers lock up and refuse to go forwards. How do you ride that? The more you irritate a rearer, the worse it may get. You struggle, they flip... Rearing is one of the most dangerous things a horse can do.