Nerf gun
The best airsoft gun you could get for $150 would probably be an Aftermath gun, but you could get a JG M4 or M16 for under $150
The one you can afford
Theres a Caw airsoft Type 100. just search that on google..
If you are just starting airsoft i would highly recommend an aeg, (airsoft electric gun) but if you are pro and experienced, a trained camouflaged sniper is the best, an invisible predator. However it does depend on the user of the gun. If you are asking performance wise then g&g makes the best airsoft guns on the market. (currently in the US)
Self protection? As in keeping robbers away from your house? I guess i would go with a gas rifle. They are often the most powerful, but are more expensive. If your are looking for home security, an airsoft gun would not be your best bet. I would go with an actual pellet gun or air rifle. Airsoft guns are more for recreation.
I say twin ozez are the best cheap airsoft guns
dont get that gun walmart has the best beginer guns
Definitely Nerf.
www.shortyusa.com
it depends on what cheap is to you
As a general rule, you get what you pay for.