Text selection (not built-in but useful) shortcuts
It is easy to select disparate, non-contiguous text in Apple's TextEdit: Just hold down the command key while highlighting each desired string with the mouse/trackpad. This action works with both plain text and rich text.

Here's a screen capture showing some arbitrary selections of discontinuous text made in this manner:


It's also easy to invert the selection: Click-and-drag the cursor over the chosen text while holding down the command key. Here's the same text after making the change: