C'mon, it's Evernote. You know, the premier note-taking app in the world?
Evernote syncs your notes across all devices, so scribbles you've jotted on your PC will carry over to your smartphone, and vice versa. The Android Evernote app does a whole lot more than basic note-taking, though. This superbly designed app packs killer search functionality, to-do checklist creation, audio note-taking, and the ability to upload camera snapshots straight to the service—a tremendously powerful feature when paired with Evernote's excellent optical character recognition technology—and it plays nice with a legion of value-adding apps and services.
A premium subscription adds even more (offline notes), but the basic Evernote for Android app costs nothing to use.