You budget will have a big impact on the answer.
The best airsoft MP7 is the WELL brand MP7.
Rainbow Airsoft is one of the best in my opinion
Airsoft GI, or Evike
I say twin ozez are the best cheap airsoft guns
See related links for some good airsoft teams.
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)
You get what you pay for.
The one you can afford
AEG? Systema
Evike.com AirsoftGI.com Airsoftstation.com There are countless others but these are in my opinion good airsoft sites.
Definitely Nerf.
The Orphus socom