Чудовище (a monster) isn't augmentative, it has no "normal" form. "Чудище" (stress on "у") means the same, it looks like augmentative from "чудо" (not a marvel, but a fairy tale monster again). Both "чудище" and "чудо" (as a monster) are obsolete, most typically you may encounter them in skazki ("чудище ужасное, чудо лесное").

There are lot's of nouns with -ище that are not augmentative (училище, стойбище, толковище).

Another interesting suffix is -ющ, used in adjectives:

Вдруг откуда-то хитрющий котище
И шипит он в длинющий усище.