In most places in iOS where you can edit text, you can tap with two fingers to select a whole line. This works, for example, in text editors like Notesy, Drafts and Byword, and can be quite a time saver. In fact, it selects the line up to the next line break; if you’re typing code, that’s probably one line, but if you’re writing prose, it’ll select the current paragraph. Very handy if you want to move paragraphs around using cut and paste.
Another place you can use it is in the URL field of a browser, where it will select the entire URL with fewer clicks than the usual tap-tap-select-all.
I use this, for example, if I’m looking at a page in Safari and want to open it in 1Password. As you probably know, apps can register particular URL schemes for their own use, and 1Password’s browser will recognise
ophttps, so you can just go to the beginning of the URL in Safari, insert an ‘op’, and you’ll be taken to the same page in 1Password (or ‘g’ for GoodReader, etc.)
The problem is that just ‘going to the beginning and inserting something’ can be a pain if the URL is long. You probably have to scroll slowly left, tap the correct insertion point, and so forth. Much easier is a two-finger tap, select ‘Cut’, type ‘op’ and then tap ‘Paste’.
If you’re doing this kind of thing regularly, you may want to set up a bookmarklet to make it even easier, but the two-finger tap is a handy thing to know in general.