Or maybe rile up the Ents and sic them on the realm. Pissed off Ents are evil.
Oh...I know! Send in a troupe of Dwarves! Or some Oliphaunts!

Lembas.

It's not overly destructive, but it's packed with canonical Elvish goodness. Plus I think it would be funny. {= )

~Neshomeh

Borrow the army Morgoth used to sack Gondolin? Dragons, Balrogs, orcs without number...

The stuff his army blew up the wall of Helm's Deep with. Then again, ordinary fire works very well.

Rocks are canonical almost anywhere.

And as I recall, fire is an effective method as well.

Not the flair of fire and flame, but it causes a lot of destruction. And goes boom.