Of all the places I explored in Paris, Le Requin Chagrin was the only bar where I got to meet and talk to total strangers. I had a very drunk, very large Frenchman talk to me for about an hour about... who knows what. I mean, the dude was *really* drunk. He did tell me I look like Hellboy. And said something about a factory he either owns or works in. But he was a nice enough fellow if a little overbearing.
Once he left, I chatted a bit with a group of students and we discussed the typical highbrow deep philosophical topics one would expect to hear in the Latin Quarter. You know, Game of Thrones, Star Trek, and Dr. Quinn, Medicine Woman.
I mention this because I really like meeting new people and talking to random strangers. This doesn't happen in Paris enough - at least not when you're a 38 year old guy who doesn't speak French. This aspect of travelling is more important to me than seeing famous monuments or going to world-class museums.
If you're looking for a friendly bar where you might have a chance to make some new friends, Le Requin Chagrin is a good bet.
Ok, the folks of Paris are gonna be miffed at me for outing this joint, but I'm gonna do it anyway. Ok, tucked away in a corner of Paris uncorrupted by huge waves of camera-swinging, sidewalk-blocking, standing-in-the-middle-of-the-street-pointing tourists is quartier Mouffetard. Hmmm, I guess I've ruined that now.
Anyway, tucked up at the top of the hill of this cool little niche in the city is home to one of the best dive bars I've been to outside of the States, Le Requin Chagrin (don't try to make any sense of the name). This is a great neighborhood-y joint, very local and cool, as in unpretentious, so check all attitudes at the door -- only the bartenders are allowed the right (just kidding). Soak up the atmosphere, soak up some beer and make friends with whomever is standing next to you.
And when the joint finally closes, or when you've had enough to drink, head downhill to look for a cab (quietly mind you, people do live here you know). But before you go home, the chicken rotisserie guys should be starting their day (yep _that_ early in the morning). Try to talk one of 'em into selling you a freshly spit-roasted chicken and sit at a nearby fountain (there's always one in Paris) and split it with your friends or other drunk strangers who are headed home too.
An English-type bar (very limited food options) in Place de la Contrescarpe with a friendly staff and a good happy hour. Grab a beer and sit outside and check out all the people going by. Great place to stop after a day of walking around St. Germain and the Latin Quarter.