Must Have Apps from the Android Market

Google Sky Map
Key Chain
Angry Birds
Alchemy
shazam
Nook app

I love words with friends, solitaire, word search, and tic tac toe. All free. Not sure about games for your boy.

bubble pop plus
advanced task killer (helps save battery life)
jorte (calender)
angry birds
battery indicator
coloring
wheres my water
Books by mercer mayer? When I get bigger etc.

Angry birds
Solitaire
Flashlight
Fooducate
Google Skymap
Word Search
Crossword of the day, Shortyz
GasBuddy
Google Translate
Taskos and Memo--BOth if these allow you to use your phone as a grocery list.
Talking Tom and Talking Gina

Angry Birds
Angry Birds Seasons
Angry Birds Rio
Angry Gran
Greedy Spiders
Farkle Solo
Mancala
Glow Puzzle
Rush Hour Free
Where's My Water?
All of these are free. Also the Android Market has a free application every day. I have the paid version of some games for free from there. My 7 yr old grandson loves Angry birds, all three versions, Greedy Spiders and Where's My Water? In fact, I only let him play when we r out or I would never have any battery for my games!

Any or all the Angry Birds
Farkle would be fun for your son
Triple stack is a good card game too
Words with Friends if you like scrabble
PicsArt, if you like taking pictures with your phone, it allows you to do collages & a lot of fun things, and you can pull pictures from many sources other than your phone
Cloud print if you ever want to print anything from your phone
Out of Milk, its an app that you can keep your grocery list in, you can even put prices of specific items & it keeps track of what your spending
Craigslist if you use that a lot
Ebay
Bump, if you know someone else with a droid that you would share things with, pictures, apps, contacts etc, you can "bump" them to eachother. My mom & I use this one a lot.

Have fun :")

I like all the ones mentioned but I want to add another that turns your phone into a flashlight. I use it when I walk my dogs, as a light to get my key into the door lock when I leave the porch light off, find what ever I dropped..... It is called brightest flashlight and its free!