When a character is set to use a weapon type they normally do not use, it appears they automatically use
Marth's animation (which is probably the first animation in the set of animations, which explains
why it is used at default).

Sword- Marth Attack Anim
Lance- Marth Attack Anim
Axe- Marth Attack Anim

Long-Range Weapons: Null Range Attack (shows range animation without any hit, HP depletion, etc., unless a magic sword is used)

Bow- Null Range Attack
Magic- Null Range Attack
Staff- Unable to fight with

The exception to this is that the unit already has an animation set to that weapon (Sheeda doesn't use Marth's anim for lances because she is set to use her Pegasus Knight animation).