About five years ago, my Motorola RAZR Platinum was stolen by some jerk so now I refuse to go without Lookout Security & Antivirus for this reason. Especially now that phones are getting more expensive.
Also, I tend to listen to a lot of music on my phone and dislike the preset equalizer on my phone, especially when using my Heartbeats. So I first installed Equalizer by Smart Android Apps, LLC (which, sadly, didn't work with the stock music player) and then Android Music Player by JRTStudio and it's crazy the stuff I can hear now on songs. Backup vocals and subtle instruments. Definitely recommended if you listen to music that involves headphones or hooking up your phone to a stereo.
I also EasyTether Pro if I ever need a connection on the go because the root wifi app I have wasn't compatible with my Note 2 last time I checked.
Pixlr Express by Autodesk Inc is a pretty cool photo-editing app and I'm surprised it's actually free.