Britain has a few...
14 you can have some kind of job over and above a paper round IIRC. Maybe 12 or 13. Erm.
14 is also the age you can ride an electric bike (upto 300w, or a little under 1/2 hp) on the road. Bizarre but true.
15 3/4 you can join the army - and with that, it's the lowest age you can drive any powered vehicle on the road, if you get thru the requisite training REALLY fast (exempted from the usual license requirements when in the armed forces I think)
16... age of sexual consent, USED to be age for buying cigarettes, quite possibly you're allowed to APPEAR in porn (but not buy it!), ride a moped... and, at least in Scotland, get married. Maybe elsewhere too, and scotland is 15.
(see, it's confusing! too many of them!)
Somewhere between 12 and 16 you can have alcohol with a meal, so long as you're with and it's bought by an adult, in a pub. Probably 14 again - I've seen a few signs on the doors of more traditional pubs prohibiting younger would-be patrons from entry.
17, drive a car, "real" motorbikes (though there are limits on which of THOSE you can be take tests for straight away thanks to EU meddling; learner license gets you a 14hp/125cc, base level "full" license restricts you to 33hp for 2 years - ie til you're at least 19 - after which you can ride anything... though this will probably be changing again soon)
18 is the "big one", comparitively. Drinking, smoking, buying the porn that you starred in two years earlier, voting, possibly marriage, and a whole raft of other things I probably haven't even heard about. I think it's also the lowest age for getting a big-truck license (anything over 3.5 tonnes), which, uniquely, has come down from 21 in recent years.
21 brings a few things as well, but damn if I can't remember what they are. The higher rate minimum wage is one of them I think! You can do pretty much everything an adult can, at 20 1/2 years old, except be paid a sensible amount!
And if you want to hire a car easily, or get non-ludicrous insurance prices, you're gonna wait til 25 :-/
EDIT: Well, crap, appears I got ninja'd by... well, just about everybody. That's what I get for not doing ctrl-a, ctrl-c, F5 before posting.