Blink - Quick Memo.

It's basically a notes/reminder app, but in the most minimal form. White screen that you add text to that you can assign a color to (black for low priority, blue for medium priority, and red for high priority along with a push notification for any red item every 15 mins). When you're done with an item, you just swipe it down to remove it.

I like that it's not needlessly complex and can used for anything that pops into your head or a list you need to check off as you do daily tasks. What makes it cool is that you can just see everything at a glance and use the simple color system to see what's most important.