$50 and under - nothing good ( boyi dboys, well, and more )
$100-150 - jing gong echo 1 cyma (amazing guns for the price im about to get ajing gong)
$150-200 - classic army sportsline (a lower end version of original classic armysbut still a great gun )
$250-400 - Tokyo marui, classic army, ICS, KWA, and more ( the best high end guns that are actually affordable )
$400 - 800 - TOP, STAR, and more ( giant 20 pound machine guns )
$1000 -2000 - systema ( the ferrari of airsoft guns the best of the best used by police and military to train )
good luck and i would recommend an echo 1 or a jing gong best guns for the money
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
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)
I say twin ozez are the best cheap airsoft guns
dont get that gun walmart has the best beginer guns
it depends on what cheap is to you
Definitely Nerf.
www.shortyusa.com
The best way - go to near airsoft workshop, give them money and tell what do you want. If you decide to modify airsoft gun by yourself - be warned, this may ruin your gun and even be dangerous to your health.
"Systema" is by far the best airsoft gun brand out there.
An Airsoft gun