I walked into (and stumbled out of) Lefty's on my second day in Pittsburgh and it will forever be my favorite dive bar in the city--a bold statement considering the incredible number of awesome dives we have here. Lefty's probably won't ever warm your heart in the same way it does mine, but it can still show you a good time and serve up a decent drink.
Even though it's located in the Strip, which can be tourist-overload on the weekends, it's actually a locals bar that only gets crowded on Friday and Saturday nights; other than that it's you and the regulars. If you find yourself in the Strip on the weekend (and why wouldn't you?) it's nice to stop in for a Bloody Mary ($4), margarita ($4) or their signature drink, a Strong Island Ice Tea ($4). I don't think they actually serve a drink that's more than 4 dollars.
Expect the jukebox to be loud, pours to be strong, the room to be smoky and everyone to be friendly (I met my first friend in Pittsburgh at Lefty's). Someone in Lefty's once told me it was "the only working man's bar left in the Strip," and I actually believe him after meeting lots of off-duty Wholey's and Roland's employees and gypsie cab drivers there.