Since I first started out reviewing games back when I was 14 years old I would make to-do lists for things I'd need to get done for Darkstation. I continued that through high school, college, and now work. Now with the beautiful iPhone 6 Plus I began looking for an app that could keep track of a bunch of to-do's. I use the app Lift for personal goals (flossing/exercise/vitamins etc) but I wanted an app that would be a lot more dynamic. Then came Wunderlist.
What's incredible about Wunderlist is that for 99% of people including myself, the free version is more then enough. Right now I've got eight different categories of to-do lists, four of which are shared with Jenn. We have a list for travel so we can assign each other to-do's for the trip and give them due dates. We have a grocery category so if Jenn needs something at the store she can add it to my grocery list since I do the grocery shopping.
I absolutely love this app. It has a bunch of different views/settings to really customize a to-do list to do what you want it to. One of my lists are just movies I want to see. So when I'm at a theater or watching TV I can remember that awesome trailer. For work its great too. I can make a to-do for the big and small items, give them importance, due dates, and reminders. It's an elegant app that works really well. Plus they have a free desktop app that syncs perfectly with the iOS version. If you have an iPhone or Mac I'd highly recommend checking out Wunderlist. The best part of all its free.