The Pocket Shot might be a good choice if you want to add a bunny, pigeon or duck to your hiking menu and you have found perfecting your skill with a conventional sling too hard (See: http://www.theultralighthiker.com/how-to-make-a-sling/)
‘With up to 350 feet per second, equals 350 km/h, double to triple the airspeed of conventional slingshots
With 12 Joule by using the original Pocket-Shot Ammo of hardened carbon steel six times the penetration power than with a conventional slingshot. Also much stronger than almost all Airsoft, Paintball or Air-Rifles
High Precision and high rate of fire. Allows quick aiming and shooting
Minimum weight of just 55 grams and extremely compact at 6cm x 2 cm’
I might not be ‘legal’ in your particular locale, so you should check I guess.
It can also fire arrows and/or be used to take fish. I would say it might also be useful for driving away dingoes which might be following you and thinking about you as a snack.
From around $A40 (July 2017)