Ulster Museum is my favourite and the Botanic Gardens beside it.
The Titanic Building is the usual place for visitors.
Crumlin Rd Gaol is supposed to be a great visitors experience. For bars try Voodoo or Sunflower or Cathedral quarter and I'd highly recommend the Dumpling Library for food in St Anne's Square
City hall tour (free)
DC tours phone app with some free guides walks including titanic trail
St George's Market if you like that sort of thing.
Open top bus tours
