I've got two boys, 6 & 8. Here's some of our results;
RECOMMENDED:
Perplexus 3D spherical maze puzzle. The kids really concentrate when they pick this up. I love this thing!
Yam Slam A yahtzee like game with poker chips for points. Very well built and fun for all ages.
Stomp Rocket Jump or stomp on the launch pad and send the nerf like rocket high into the air.
Remote Controlled Thunder Tumbler I've recently seen them in CVS. We've had 2 of them for about 3 years and they still work and they're still played with
Zoom-O Also a 9.99 toy, found at WalMart, Target, etc.. Shoots a propeller disc into the air. Simple, but very addictive. Non-competitive and just fun.
Nintendo DS My 6 year old would bring it into the shower if he could! If I had a nickel for every time I've heard "Can I play my DS?" It's the Pokemon games that he loves.
'Dangerous Book For Boys' (or the 'Daring Book For Girls')
Building Stuff Lego Sets (Atlantis, vehicles, etc) K'Nex, Bionicles, Magnetix
MP3 players Doesn't have to be fancy. Fill it with stuff that'll get them interested in tunes; Classic Rock, 80's, 1 Hit Wonders, Beatles, Bob Marley, etc.
Apples To Apples If you've got at least 4 people and most can read (you can help to an extent), it's always a fun game.
Five Below My boys love this store.
Other notables:
20 Questions Fun for the younger kids who can read
Mr Root Beer Make your own root beer.
Rubik's Twist Easy to get the hang of, travels well.
Duds
Air Hogs They are fun and they work well, but the kids lose interest when they have to charge so much.
Fushigi = Fushi++y