GS_Dirtboy said:
The OP's original question was where to find the nightlife that Buenos Aires is famous for. There are a number of comments here that suggest specific boliches and bars. My suggestion is to hang out in Recoleta on a Friday or Saturday night. Check out the area around the cemetary. There are (were) a lot of nightlife areas there when I was a single guy.
There's also always stuff going on you should check the government cultural agenda. It doesn't take long to start finding things to do once you know where to look. There's a lot of alt guides to the city that you can pick up at bars and list what's going on, you just have to keep your eye out for them.
Frankly I'm pretty far removed from the nightlife scene now -- most of my friends are as well because it's pretty expensive. When I came things were pretty cheap for expats and at least accessible for locals, now a lot of stuff is out of people's grasp unless your someone that has lots of money or parents who are footing your tab at Kika and the "plastic" places your refer to.
Also, BA is a big city -- once it's in TimeOut, it's probably already lost it's cool. Please, Puerta Roja was sooo 2006 (haha), 878 was THE place that only the in crowd knew about, now it's just another bar who's original bartenders have moved on to other places. DuiDui I think has kind of lost it's only-in-the-know chic by now, but there are a few hidden bars around. Like any big city a cool place comes and goes, probably to be replaced by a Starbucks (I think El Diamante might have been taken over by that complex on Malabia). Places survive but won't necessarily have the cache they once had (Carnal, Bar6, Congo) or they'll have a new crowd that isn't necessarily same vibe. The original crowd graduates to a new place (Godoy, which has been there for years now and always struck me as a stuck up expensive crowd, but Weds has an afteroffice which may be good, dress up for it though). Every bar has it's night, you have to be there for the right one.
Try What's Up -- used to be pretty good but haven't used it in awhile...
http://www.whatsupbuenosaires.com/agenda
Edit: By the way, Friday has never been the biggest night here -- Weds yes, Sat yes, Friday not so much. Friday night is for being with the girlfriend/wife. Saturday night is for picking up a new girl...