Strip District. Spend a full day there. Primanti Brothers. Pamela’s P&G Diner (get there early to avoid the long lines). Deluca’s has the Steel City Breakfast of Champions. Also, the best nightlife in P’burgh is in the Strip District.
Grandview Ave. on Mt. Washington has some great overlooks.
Station Square is a happening place.
And if you’re single looking to mingle, the Port View girls are easy. “Big boned”, but easy.
Pittsburgh Zoo isn't bad, and others have mentioned the Carnegie museums.
If you're flying into the city, head to Angelia's in Imperial, PA (not far from the airport) for some superb pizza.