Many fabulous places out there! Grand Canyon is a must - with flight following for preference. You can get some fabulous views and photos.
I'd also highly recommend Sedona (eat at the field - the food is excellent); Meteor Crater (overfly); Sunset Crater (actually a volcano, visible only from an aircraft); Big Bear (get them to stamp your logbook); Catalina Island; Palm Springs; and if you have time, go up the coast from LA to Monterey.
I've promised myself to go back there next year.