Well, I think that
?"One Note" is a perfect for "Google Keep", it helped me a lot when I switched from android, he can also check Tinydo if he needs a simple clean UI to do app.
?adidas miCoach / 6 Week Training / BodBot Personal Trainer (it's really a taste / purpose thing)
?WPCentral app!! One of my favorites.
?2safe for his passwords
?MyTube the best YouTube app on WP8
?Digitally Imported / SKY.FM Radio / TV Show / CineTube for music and media
?Camera360 / Picsart / Fhotoroom / Photosynth Sophielense HD as the best photography apps
?Bing's Collection of apps (News, Sports, Weather, Finance, Food & Drinks...)
?NBC News, Bloomberg, FlipMag Beta, Phonly for news
?Battery Performance / Insider / Cal Calendar for accessory apps
? Get Them All and wpTorrent for downloads.
These are my personal favorites, still, there are tons and tons of great apps on WP8.. I avoided to mention the obvious ones like Facebook, Twitter and Instagram Beta. Hopefully this will help a little bit.. Welcome to windows phone 8 buddy!!!