You may want to change this to a PreHook, Otherwise Falchion and Butterfly will have bugged animations.
It took me a while to figure out that it was just a simple change to prehook.
Edit: (Its really as simple as this and you will get perfect results everytime without glitches)
PHP Code:
public OnWeaponEquip_Pre(iClient, iWeapon)
{
RemovePlayerItem(iClient, iWeapon);
SetEntProp(iWeapon, Prop_Send, "m_iItemDefinitionIndex", g_iItemDefinitionIndexes[A_FANCY_INDEX]);
}