Here's My List:
Tack Trolley Thingy:
This thing is great! I came across it recently (available from Robinsons). It's the easiest way of carrying all your clobber from tack room to stable and means you don't need to have saddle racks all over the place or put your saddle on the ground, scuffing it. For £36 it's a bargain.
I've had one of these for ten years now and is probably the best tack investment I've ever made. They are one of the most expensive and at today's prices will probably set you back about £3.5K new, and the good 2nd hand ones are fetching over £2K. Mine is still in near mint condition and the most comfortable saddle I've ever ridden in (for both me and the horse). There are plenty of new saddle makers coming out with decent saddles at more competitive prices, so I may go for a different brand for my new dressage saddle, if I can't find a nice second-hand Devoucoux one (purely for financial reasons).
Point Two Air Jacket:
I love technology, but even more so when it has really practical use. These Air Jackets are designed to slip over your body protector, and they inflate before you hit the ground in the event of a fall, providing an air cushion for landing, think of it as a rider's air bag. They really are life savers and a must for everyone. (pic to follow)
A silly thing I know, but these whips always tend to break because they're so long. I bought one about 15 years ago and still have it today. Being two-piece means it's super easy to store, take to events, and carry with you without spooking the horse. About £8. Probably available from most good tack shops and online stores.
Another recent purchase at about £100. This is like having a lunge cavasson and bridle in one, but nice and light, and really well thought through design. I use it whenever I want to lunge before riding. Works a treat and saves time. Read more about it from the designer William Micklem, or my experiences.
Having a video camera can be a bit of a luxury, but I find it invaluable to review my riding as often as possible, as it can be very difficult to see where you are going wrong from the saddle (it's easier to see what's going right from the saddle). You should be able to pick up a decent second hand one for about £80, and if you do invest in one I highly recommend getting a tripod (about £35+). I also own a mini HD Helmet camcorder too, which is proving practical as well as fun.