Lowenbrau, Bittburger, Guiness & Weisteiner are my faves right now... I like to mix & match imports from the LCBO... Locally, I dig Mossehead, PC Honey Brown (when finances are tight), Creemore & Sleeman's.
I like the steamwhistle, but only in bottles. It's brutal on tap. I've been really digging the Mill St selection these days too. The tankhouse ale is great in bottles, but is especially wonderful on tap. My staple for a while now has been grolsch though.