I had two fun wins on dominions.games today, both featuring Rats:
First game: Worker's Village + Pooka + Rats + Transmogrify
I got two transmogrifies and would use them (usually on Rats) to start off my WV + Pooka engine on rounds when I didn't get both a WV and a Pooka in hand. WV allowed me to keep myself in Coppers to feed to Pooka and Rats, and I could use my Cursed Gold freely and feed the curses to Rats.
Second game: Hunting Party + Rats + Fortress + Warehouse + Forge
Hunting Parties would seek out my Forge, and I'd forge two rats into a province, pretty much every turn. Fortress provided a no-risk way to keep the Rats gains going once my deck had been pretty thinned, and Warehouse let me continue drawing my whole combo even late game when I had a ton of provinces -- it was a Colony game, so I bought out all 8 Provinces, which obviously ordinarily slows you way down.
Both were against opponents significantly lower-level than I was, so a more efficient opponent might've prevented these fun combos from being game-winning (especially the second game, when my opponent didn't really contest Hunting Parties at all, which was clearly a mistake). But my view is any time you can turn Rats into profit, you gotta try.