Palos Verdes (PV) peninsula, hands down. Not a town, per se, but Rancho Palos Verdes (RPV), Rolling Hills, Rolling Hills Estates, and Palos Verdes Estates (PVE) comprise the peninsula's municipalities. Redondo Beach is the beach city at the base of the peninsula/hill, and that's a great small city. Closest to PV is Riviera Village, part of Redondo and a little bit of Torrance, and this area is called the Hollywood Riviera. It has a real resort-town vibe to it, but is really laid-back as well. This whole area is hands-down the most beautiful place I have ever seen, and I can't believe it took me 5 years in SoCal to discover it.
Bob, I think Pasadena is gorgeous. With the rolling hills, the New Deal-era bridges, and the new vibrant downtown centered on Colorado (Old Route 66), Pasadena is a great place for history buffs and scenic tourists alike.
While Orange County has some beautiful coastline, I don't think any of it is better than the south bay/PV peninsula, and the people who live there are so damn plastic and superficial that while aesthically beautiful, my judgment of the area is so negatively affected by it that I don't like being there. If you like new money assholes and the golddiggers that married them, then you won't have a problem with OC, but I can't deal with that. Laguna Beach and Newport Beach are incredible to look at, but the people...argh!
Up in the Santa Monicas, Woodland Hills and Calabasas are both beautiful, but they're a trek. I just love PV because it isn't too far removed from anything, yet it's great relaxation. PV was also one of the earliest master-planned communities, and it has a lot of character unlike over-planned Irvine. Olmsted did a great job, especially with the landscape architecture.