If you keep lots of info in the Notes app on your iPhone or iPad, you're probably aware that you can use Siri to create new notes. To do so, invoke Siri (by holding down your device's Home button until you hear the beeps), and then just say "Note [whatever information you need to save]." That's pretty neat, all right, but did you know that you can search through your notes with Siri, too? All you have to do is say something like "find my note about [whatever]."
Hey, don't mess with my favorite characters, or I may have to get virtually violent.
Siri will show you the notes that fit the search term you mentioned, and from there, you can touch any of the results to be taken directly to the matching note in your app.
The only caveat is that Siri uses what you say as keywords for searching, and the service isn't great at knowing what you meant versus what you said. For example, if I ask Siri to find my note on "fictional people I need to punch" instead of "fictional people I want to punch," it won't know what the heck I'm talking about. So if you're having trouble finding a note, give less information rather than more—ask to find your note on fictional people, say.
Anyway, another groovy thing you can do is add text to your existing notes through Siri. You'd say something akin to "Add [information] to my note on [keyword]," as below:
You can, of course, use Siri to search all sorts of other personal info, such as your Reminders ("Do I have any reminders about [subject]?"), your Calendar events ("Search for any events with [person]"), or even your emails ("Find emails from [person]"), but for me, the Notes search is far more useful than any of that stuff. At least I think so, and I'm the one who's writing this tip, so there.