Do you feel most checklist tools are too rigid and/or too specific to use? Pen-and-paper is still quite possibly The Method? This tool aims solving that: create list, use 2 types of checkmarks, and optionally let you tag a photo (by file, and by camera if your device offers it)
The App "2me" ("Ame" in italian) allows you to set one or more default e-mail addresses to send any text element can be shared by other device's applications (web pages, tweets, text notes ...)
Changes your lock screen PIN every minute magically.