Barbarian: "You young whippersnappers don't know what it -really- means to be a Berserk. You'll never be a -real- Berserker if you don't learn to control your temper!"
Fighter: "Age and Cunning beat Young and Fast any day of the week."
Rogue: "Yeah, yeah, yeah. MOVE. I'll let you know when it's disarmed."
Druid/Ranger: "I've been guarding this land since before you were a twinkle in your Daddy's eye, boy!"
Paladin/Cleric: Just complain about how young people have no faith, don't read the books, and generally disrespect their elders.
You can do it with any class, really.