The most elegantly powerful note-taking app!
UPDATE: I love the new ability to have multiple images or videos per note! I've been using it to make notes into little photo/video albums! I also really like freehand sketching on images.
Moe's Notes is easily the most elegantly powerful note-taking app out there. No other app so seamlessly incorporates audio, video, photography, GPS coordinates, and tags into a note. And no other app allows you to filter your note list by text, tags, date/time, and GPS, enabling you to find a note long after you took it, with only a vague idea of when/where you took it.
And the audio editing is something else! You can quickly edit a long recording down to just the bits you want. (There's even a Strip Silence command that does this automatically.) Then for fun, you can play the audio backwards, sped up, or slowed down!