Leonardo Express at Fiumicino Airport
Nonstop service from Roma Termini for 14.00 E a head. Not exactly fast - more a sort of steady ramble.
Buying tickets at a machine and then immediately having to validate it seems silly. At Termini it also puts you at the mercy of the people who force their "help" on you, expecting some financial reward. FS and their police force should crack down harder on these pests, some of whom are engaging in bag snatching and demanding money with threats. More attention to this crime would be better PR then persecuting "fare evasion" which is often simple machine malfunction.