iOS: You won't find a shortage of fantastic task management apps on the iPhone, but Finish takes a slightly different approach. It organises your tasks into three separate timeframes and automatically lets you know what's important for that exact moment.
Unlike a straight-up list, Finish puts your tasks into three categories: short term, mid term and long term. As time passes, the most important tasks slide up the list so you always know what you need to do right now. Finish also has a "Focus Mode" that only shows you the most important tasks in each of the different timeframes. Finish doesn't have a lot of features, like syncing or cross-device compatibility, but it does a great job of telling you what's important to do right now. It's a little different than most to-do apps out there, so it's worth a look if you're hunting for an app that does things a little differently.
Finish for iPhone: Timeframe-Focused Todo List [iTunes App Store]