Favorite thing: While you are in Rabat, you have to see St. Paul's Church in the main square. It dates from the 17th century. Also visit St. Paul's Grotto beneath the church. It is just next door from the main entrance to the church. There are underground Christian cemeteries dated from 100-400 A.D. Visiting catacombs is free. The guide will tell you the short story about them. However, when you leave, tips are appreciated.
Just hang around the city ... it's a piece of unique mixture of arab-euro architecture with some very good ald stuff (I remember some very nice bars) ... and do not forget to visit Mdina.
Fondest memory: The way I travelled there: by maltese bus driven by a real-crazy-smart maltese driver !!!
Favorite thing: Close to the St. Paul's church in the main square you will see Parrucan - a confectionery of traditional Maltese cakes and nougat. It's always interesting to taste the local food and sweets:)