I carry a close-focussing monocular. One advantage of monoculars is that you can get ones which focus on things less than a foot away, so they act as magnifying glasses or (very weak) microscopes. You can get a good look at, eg, insects which you might not want to touch.

For distance vision they are useful for checking out routes and signposts so you don't waste time going the wrong way. You can also check out other people before you get to them, if you think they may be hostile. If you watch 24 you'll know that Jack Bauer is always peering through his monocular.

I use an 8x20 Gallery Scope from http://www.opticron.co.uk/