Lets see. Mauville is pretty common because of the day care, then theres the Cycling Road with Slateport at the end for when I'm egg hatching. Then theres Fallabor town, which I hate, but my friend's secret base is there so I often battle him. And like a lot of other people have said, Lilycove is another one. Usually it's for buying Fire Blasts and talking to the move deleter so I can get my Pokemon onto Diamond.