What would my morph be? If I had access to the Time Matrix, a mastodon or sabertooth tiger. If not, an assortment of humans to hide my identity while I piled pain on the Yeerks with a Dracon Beam and some M16s. I know that morphing human is unethical, but then again so are the Yeerks.
Edit: Also some really sneaky creatures for when the going gets rough and I have to retreat. Such as a rat, or a worm or something. Also, an Octopus.