Repairing small damage to outside corners. Plaster walls.
Use plaster, 2-part body filler will be just as likely to fall off upon impact and is more difficult to use (IMO). 

Rough up the areas around the repair to improve adhesion. Moisten the existing damaged area before carefully applying plaster repair. Mix it to a firm putty consistency then use a moistened wide putty knife to "feather" the plaster back onto the adjacent wall areas. Sand smooth.

You might consider using a corner protector for areas subject to frequent bumps, they come in all colors and sizes including clear: