1. Allowing us to express movement through text
    *sigh* *shrug* *yawn*
  2. Keeping things PG
    Don't you f*cking forget it, b*tch
  3. Implying things aren't all they're cracked up to be
    Only 19.99*
  4. Alluding that there's more to a thought*
    *like right now, see?
  5. Saving us from appeering idiotic
  6. Thwarting would-be crooks
    Password: ***********
  7. This emoji
    *・゜゚・*:.。..。.:*・'(*゚▽゚*)'・*:.。. .。.:*・゜゚・*
  8. Curbing prank callers
    *69 that shit and BAM, you've got the call back number (admittedly, the asterisk has lost some of its power in this department post-caller ID)
  9. Enabling prank callers
    *67 then dial the number and BAM, you've blocked you callback number.
  10. Allowing us to virtually kiss
    Suggested by @ChrisK
  11. Kurt Vonnegut's asshole *
    Suggested by @hannahstark