I understand some enthusiasts get very emphatic about this issue, but I can only speak to my own very limited experience. The tool immediately to my hand now is a Leatherman PST, easily about ten years old or more and still not showing many signs of age. As I understand it, it's the very basic original Leatherman model. It's paid for itself many times over in simple ready convenience and utility. I see there are some very fancy and complicated multitools around. I have no comment about those, as I've never used them. I would say that my comment was based only on my experience of often needing quick access to a variety of screwdrivers, or pliers, or a bottlecap opener, or wire cutters, or the knife. (I personally haven't used the file very much if at all.)

I don't have any knowledge of UK knife laws, but the thought of them saddens me, because a knife as a basic tool is useful in so many, many ways. The number of times in which I've been imminently inclined to use my knife as a stabbing weapon in real life has been exactly nil (it wouldn't have been practical in any case -- the Leatherman is hardly a switchblade. For legal defensive purposes, you might be just as well off carrying a sharpened wooden pencil) but I've been happy to have the power to cut inanimate objects uncountable times.

I'm a huge fan of the Leatherman Micra, as it's trivial to have it with basically all the time. I've been surprised with how efficient the screwdrivers manage to be, and at least for me, it covers everything I'd plausibly run in to while out and about (I have a separate one for doing electronics, that includes wire strippers and such, but I've never run in to a situation where I needed that one unexpectedly :))

The tweezers are a bit awkward, but I've used them to remove a number of splinters, so they definitely can do the job (I go barefoot, and having this thing around is wonderful for that alone...)