Avalanche is not a good move for Weavile. The power doubles if the user took damage first, and Weavile is a fast Pokemon. You can teach Ice Punch to Weavile by Egg Move, or, if you have some other game with a move tutor in it, you trade Weavile to that game, teach it Ice Punch, and trade it back. Note: You can only do that if you have HeartGold, SoulSilver, or Platinum as well.
A really good move set would be
-Ice Punch (STAB+high power+Weavile's good attack)
-Night Slash(STAB+high power+Weavile's good attack+high critical-hit ratio)
-Some good physical fighting type move (Hopefully high power+Weavile's good attack+ advantage/defense against Normal,Ice,Dark,Rock,and Steel types)
-Aerial Ace(Defense against Fighting-types+Weavile's good attack+no-miss move)