Le Sainte Elisabeth is known for its legendary terrace. It's not as grand as the crazy one over at Saint-Sulpice, but its size and in-the-corner-ness does give it quite the kick.
The inside is pretty nice, and it's got that nice woody bar feeling you expect to see in a proper pub. If the first floor is full (and chances are it will be), there's also a pretty big second floor with much more space. The music at the place is pretty loud though, so you'll have to get pretty up-close-and-personal if you want to talk to someone.
They turned their fireplace on (with FIRE!) when I was there in the winter, and that was a pretty good spot to hang around until the staff forced us out cause we were blocking the entrance. Oh also, just a heads up, the terrace is closed in the winter.
The entrance to the bar is in a small, fully graffiti'd alleyway off of St Catherine street. It's hard to miss the entrance on a night out since there's usually a crowd outside and the graffiti on the wall outside is pretty neat.