It really depends on how much money you are willing to spend and what type of stuff you are willing to put up with. If you don't mind the extra mass and cost, for ~$500-700 you could get yourself a decent gas rifle with an external regulated Co2 or Nitrogen (aka HPA, high pressure air) setup. The external air setup can be bulky, though there is some pretty cool stuff out there if you don't mind it. Here's some examples for you:
Escort Mp5a5 - External air, gas blowback. I have one and the blowback is impressive; more than some 22lr handguns. Full metal upper receiver and pretty much every component that should be is metal (some have plastic front sights). Lower receiver, butt of the stock (rails are metal), and foregrip are all a reinforced plastic.
Sun Project M4a1
Maruzen Mp5k - Internal gas, blowback, much simpler than an external gas setup and significantly cheaper (you can find these anywhere from $150-200 usually)
Just FYI, pretty much all of the electric airsoft handguns out there are incredibly weak, don't have much range, and are really useless if you are going to actually play airsoft. I would avoid them.
Here's a decent retailer from the US if you want to get a better idea of what type of stuff is available out there:
Airsoft Extreme
There is a ton more stuff out there than that retailer has (and a ton more US retailers as well), and I'd really recommend browsing an overseas retailers website to get an idea on the crazy amount of airsoft stuff out there. Here's a couple:
Redwolf Airsoft
UN Company
There is a pretty insane number of airsoft guns and accessories out there, so pretty much any model of gun you might want a replica of, you will probably be able to find. I mean there are gas powered M1 Garands, M1 carbines, M2 carbine (yep it's full auto), winchester lever actions, pump action and semi auto shell fed shotguns, gas and/or electric M134 Vulcan mini guns (and they shoot 4000-6000 bbs a minute like the real thing)..........Oh yeah and I'm not even getting to the airsoft claymores, hand grenades, M72a2 LAWs, M203 attachments that shoot rubber/foam objects or have multiple barrels and fire bbs like a shotgun.
I've been playing since I was a kid, though some adults think it's a bit ridiculous, grown men running around a forest playing army and all.
When I'm not shooting real steel stuff, I look at it as a cheaper hobby to keep me busy and physically active (especially considering the prices of 45acp lately). If anyone has any airsoft related questions, feel free to ask as I've been into it for ~9-10yrs now and like to think I'm fairly knowledgeable on the subject. Here's a pic of my Escort blowback Mp5a5 for sh*ts and giggles:
Mp5a5