There are several super-strong acids that exist, with highly interesting properties.
Sulfuric acid: The most common of the strong acids, it is the acid that all other strong acids are compared to. Sulfuric acid does not have an extreme ability to protonate substances, but it is a highly reactive substance.
Magic acid: Containing antimony pentafluoride and fluorosulfonic acid, it was called this because of its ability to dissolve hydrocarbons such as paraffin wax. Dissolving a candle in this acid was a magic trick.
Fluoroantimonic acid: This acid contains antimony pentafluoride with hydrofluoric acid. This forms the extremely stable cation SbF6(-), leaving the hydronium ion quite bare.
Triflic acid: one of the earliest discovered superacids, this acid is relatively tame and in common use, but is still much stronger than sulfuric acid.
This is nasty stuff.