Rodents of Unusual Size?

(I'm eating lunch at my desk, today.)

Buttercup: We'll never succeed. We may as well die here.

Westley: No, no. We have already succeeded. I mean, what are the three terrors of the Fire Swamp? One, the flame spurt - no problem. There's a popping sound preceding each; we can avoid that. Two, the lightning sand, which you were clever enough to discover what that looks like, so in the future we can avoid that too.

Buttercup: Westley, what about the R.O.U.S.'s?

Westley: Rodents Of Unusual Size? I don't think they exist.

That's what immediately popped into my head when I heard this story:

A giant rodent five times the size of a common rat has been discovered in the mountainous jungles of New Guinea.

The 1.4kg Mallomys giant rat is one of two species of mammal thought to be new to science documented on an expedition to an area described as a "lost world".

Ah, well. I thought it was amusing. What caliber do you think would be best against R.O.U.S.'s?

UPDATE:  Original JSKit/Echo comment thread courtesy of reader Jim Hardin is available here.