Rimfire and/or Centrefire...??
Rimfire obviously the likes of a .22LR for one.
Centrefire could be any number of calibres like .222R, some say that "Underbore" calibres show the best barrel life but it's not that simple. One chart that lists "Overbore" cartridges is here
http://www.accurateshooter.com/technica ... y-formula/ so at the top of the list starts with underbore cartridges.
One example is what I have and use for out to 300m Hunter Class ie Score Target being the 30BR. So far in my investigations I have never found or heard mentioned anyone wearing out a barrel, more to the point being hasn't worn the "throat".
The wear is so unlikely that a Gunsmith will trim most or all the "Knox Form" off the chamber end of a barrel to make weight with a heavy straight profile barrel. Any Gunsmith I have spoken with has never heard of one being re-chambered through wear to the throat.
Some years ago one very high rated competition shooter reported being way past 8,000 rounds with his barrel and the bonus on top of that is it's also very kind on cartridge cases and his initial 150 cases were still being used. That's over 50 reloads per case and still going years later and still winning competitions.