I use an exchangeable tip Royal live center and it is very useful. It has a standard tip, a tip that can be machined as an extended tip for small diameter work, a bull nose and inverted bull nose. The set is match-ground to the live center so it is very accurate (TIR 0.00005"). It is also very expensive. Nice thing is that if you make or cut your own tip, Royal will grind it to match the live center for free to maintain the accuracy of the live center.
With that said, the standard 60 degree tip is used 90+% of the time and it is far cheaper to buy a good standard live center. Royal, Riten and Rohm are all very good.