GitHub - Hovering over relative timestamps shows a tooltip with the absolute timestamp (UTC).
Apple - searching for colloquial or rumored product names (such as iTouch or iTablet) refers you to the appropriate products.
Kickstarter - The email sign up field proposes related email provider is it thinks you may have mistyped your email.
Safari 6 — After dragging a link to the bookmarks bar, you can immediately change the name of the bookmark.
OS X - Finder prevents you from accidentally modifying the extension when renaming a file, but only for known file types.