Exotic URIs, e.g. tel:, xmpp:, nv:, sip:, etc.
There are ample of different URIs out there: https://de.wikipedia.org/wiki/Uniform_Resource_Identifier#Beispiele

``` 253:
   anno1 tel:+491232345643

taskopen 253 -> call is being initiated
```

nv:// is application specific for Notational Velocity, personally the URI support allows a seemless integration with taskwarrior

geo:48.33,14.122;u=22.5 makes sense, Google Maps or OSM is opened.

Considering mailto:John.Doe@example.com could speed up drafting emails.
