Karras Brothers is a small bar next door to the Atwater Brewery along Jos. Campau down by the river. The staff there are the nicest bar staff I've ever met and the bar is pretty damn cool. Every once in a while, they even host a Flickr art show. The bar is laid out pretty cool and the upstairs is great in warm weather.
The only downside? No draft beer or cheap drinks, however they make up for it by having incredible prices on upscale whiskeys and bottled beers.