Drink alcoholic beverages. And pretty soon you'll have to be 21 to buy tabacco. And weed will be legalized here soon most likely. (California) though not in time for my birthday.

Ireland has it at 18+. There are definitely other countries that have it at 21+, however I do not know which country has that as a law.

one of the tags is "beer" on the post and most countries don't have a legal drinking age of 21 but some do.