Underrated Pokemon?

I feel like HGSS has always been a really oddly structured game to me so I always wound up just picking the same mons to have an easier time: Typhlosion/Feraligatr, Heracross, Ampharos, Gyarados, Nidoking/Queen to name a few. I feel like there's a bunch of pokemon that seem cool but I either never knew what to do with them or they're just annoying to get.

What are some underrated mons you guys like to use for the main story up to the E4? I've been thinking about trying out Ambipom, Girafarig, Skarmory, Poliwrath and Ninetales.