Depends on the budget you have, but probably a Hot Wheels loop track will make him happy and keep busy, or something like that.

Based on this video of this kid who found his mum's dildo, apparently double-dildos.  The kid was going wild playing with the thing.  Even dad got a laugh out of it. 

But I think those are probably an expensive gift for a 7 yo old.

EDIT:  I'd try to find out what his interests are.

The 2DS + Pokemon

or 3DS if you trust them not to snap it in half and they are old enough for 3D (I think 7 is old enough) though you can turn 3d off in the parental controls anyway.

Start the addiction early.

My nephew is over 5, but I can't go wrong with LEGO's. His soft spot are trucks - fireman, police, garbage lol For a good impression, go for the bigger set ;)

This is a good idea

I didn't go with Legos. Too many options. I talked to his mom and found out that he likes Superman, Batman, and Star Wars. Grabbed a Star Wars Light Saber. Mission complete!

http://www.youtube.com/watch?v=XgQHbHLUW2s

I got my SNES at seven. Get them a Wii U. My parents hated when I started playing the Playstation, it was either Nintendo or nothing at all, so Nintendo is a great start for children.

On one hand, I'm glad you joined because of this thread.  On the other hand, if you wanted a serious answer, I'm sorry!  We're a loveable but not very helpful bunch.  :(

Hey.  I'm telling you, that kid had a blast with that double-dong dildo.  I don't have a link to the video but the kid running around jiggling the thing, his dad just loosing it laughing, and his mom flustered, running after him trying to stop him.  In a way it was reminiscent of Benny Hill, which no doubt is meaningless to most of you.

Funny as heck.  A gift a kid loves to play with, and mom (or dad) can play with too.

2DS