IdeaPad
Super simple and straight forward, this app just lets your record an idea as it comes. You have really basic options to “add new idea” or “view ideas,” so the simplicity of this app is really its best feature.
Notes
Default iPhone app, but totally works for quick list-making and recording. I love the look of the yellow legal pad, and save everything from grocery lists to random quotes I read/hear.
Evernote – capture notes and sync across all devices. Stay organized.
This is one of the most popular productivity apps for a reason – it’s an amazingly seamless move from the website to the desktop app to the iPhone app – I’m sure the iPad users would say the same, but your account syncs between all extensions making it super easy to see your lists and notes from any login point. Super valuable if you’re switching between devices on a regular basis.