Have you ever tried to reverse in the railway station car park in the middle of winter with people and cars milling all about when the windows are fogged up, it's pitch black and you've not got any reversing lights? I have, too many times! I decided to fit a pair of front-sidelights to the back of my Land-Rover as reversing lights. Very simple job to do! I mounted a microswitch on the gearbox gate for reverse gear so the lights came on when I selected reverse, but I found this switch got gunked up and wouldn't always switch reliably, so I've now got a switch on the dashboard instead.
I put higher wattage bulbs into the reversing lights so they are bright enough to see to reverse by. They do get warm if you leave them on for a long time, but I don't normally reverse for very long!
Do you hate tailgaters? People who follow too close drive me mad. Wouldn't it be nice to have a pair of nice bright white lights on the back of your vehicle just at the following drivers eye level? Purely a hypothetical thought of course! The other purely hypothetical situation you might like to consider is the guy who has been following 2' off the back of you and who is now stuck behind you at the traffic lights. Before the lights change green, rev the engine bit so the guy behind knows you're going to zoom off just as soon as the light change. As you go to select 1st gear, flick on those nice bright reversing lights (it helps if you crunch the gears a bit too as if you aren't familiar with the gearbox) - discretely watch Mr Tailgaters face in your rear view mirror as he wets himself - then as the lights turn green zoom off forward. (Don't forget to turn off those reversing lights!)
NB: Don't do this! It's bad and wrong!
HOT TIP: If you fit manually switched reversing lights, by law you should have some form of warning on the dashboard to remind you that they are switched on.