For a warrior either Smite's or Nightreaver is good. Smite's for the stats and reaver for the proc. Reaver is probably more burst DPS, if that matters to you. On enchants however, I'd take crusader as a warrior no matter what. It heals you and gives you 200 AP (100 str). Nothing beats that imo.
With a rogue I'd go for Lifesteal or Crusader, since rogues get 1 AP from one str, you'll get 100 AP from each weapon if you DW it, rather than a 15 AP all the time. Not to mention the heals.
Lifesteal is obviously also good, but seriously: My opinion is that nothing beats crusader for melee twinks. Shammies, along with warriors, gain 2 AP per 1 str. Pallies I'm not sure, but they should get 2 AP for 1 str too. Rogues only get 1 AP from both 1 str and 1 agi, but they're the only ones who can DW at lvl 19, thus getting 2x crusader (= 1x more heals and equal +AP to the other melee:ers).