I'll beat Wasabi to this one, Tempest on 30th and 8th is an awesome spot. Been back there once and want to head back next weekend. The people that were there were pretty cool.
Tammany Hall was a favorite during my early college years, it's on 53rd and 3rd.
If you got money to burn, check out the W hotel's Whiskey Bar. It's at Broadway at 47th, and it's a pretty good spot, the DJ's are usually pretty slick.
Two fridays ago we hit this other spot, Kanvas, on 24th and 9th. It's very small, but the friday after work timeslot was pretty packed. My boy managed to pick up two girls at the same time, we were pretty awed.
Of course, our favorite location at the moment is Buster's Garage. I forget what the cross street is, but it's just off the Franklin street station on the 1/9 line. It's awesome, Friday happy hour is you pay $10 and you get all you can drink. The waitresses are insanely cool too, which is probably why we keep going back there XD.
I also like Sutton Place, thats an awesome bar. I think its on 52nd & 2nd. I went there a few times, and its a great time. Big place, lots of chicks, and in the summer they have a nice roof bar that you can hang out at.
Ah, that's what that place is called. Yeah I went there Thursday as one of three places we hit that night. It was PACKED at the time, but it was a sausage fest. Incredible view of the skyline though. That place is definitely good times.