myTube (worth having WP just for this)
Start Screen Clock (aka Tile-clock)
Car Dash (I also use this as a glance-type screen when charging)
TuneIn Radio
Weather Channel tile, official (kinda ugly but gives wind speeds)
White Screen of Life (flashlight for L520)
Cellular Data (data switch by MSFT)
Fast TV Listings
Drudge Reporter tile (does not use the ugly Drudge motif)
wpTorrent
P | Cast
Sharefolder Explorer (connects to your network)
Media Center Remote
RAD Now (radar)
gMaps
GPX Viewer (hiking maps)
Basic Timer
SpeedBuddy (speedometer and compass, works in the car and hiking, L520 has no compass but this one works if you are moving)
Lock Screen Text (shows email and phone number if lost)
Various banking/shopping apps which I put in a folder
All the free Nokia apps like Here Drive+
Pro-tip: You can create an icon for a pinned web site by zooming in on the site's logo.