Ratchet & Clank 3: Up Your Arsenal

You can get the Qwack-O-Ray on Planet Aridia for 200K (180K with discount) from a vendor. Once you get it, head back to Daxx (preferably immediately) and go up the path to the left. See the red flies? Use your Qwack-O-Ray to turn them into Ducks. There are quite a few of them so just keep zapping all that you see until the Skill Point and trophy unlocks.

If you wait until you level up the Qwack-O-Ray, it will be much harder as the ducks will lay explosive eggs that can destroy the flies, home into them and later turn into fireball shooting bodyguards. For this reason, it's best to get this out of the way as soon as you can.