Undertow is underrated (and surprisingly hard to find)
Last year, I was on a big Alternators kick. This year, I've started to crawl back to Power Core Combiners. Of the ones I've gotten, I was shocked to learn that they did a speed boat I didn't know existed as a kid, and that I was able to find him in a cheap lot of 6 figures on Ebay for the same price as the cheapest Undertow by himself. So of course I nabbed him, and he's probably my favorite ahead of Steamhammer. Just a really solid guy, and a lot better than a lot of the janky PCC Commander figures. I would love to get a Heavytread too, but he is even more expensive thanks to that upgrade kit, so I'll hold out hope that I find him in a lot like I did here.
It was surprisingly difficult to find instructions for this guy, especially because nobody bothered to archive them like the rest of the PCC guys on Unicron.com or even Hasbro's official instructions site, so I had to go off of the photo on TFWiki to figure him out (it's a scout class. It wasn't that hard, but still.)