First beer I had once I turned 18... Let me think for a second.
A few months before as I was 17 I had had two 3.5% pilseners (you can buy 3.5% at the grocery store at 18 but nothing stronger than that here, the party people were lazy, you also need 20 to buy from the alcohol monopoly, which has the strong stuff)
After that, I'm not wholly sure. I think I bought a few 3.5% to try for myself, just to get an idea. I realized that I probably preferred ale, but I was undecided. What came after that... I believe it was a dark Czech lager, Bernard, at a Czech restaurant. Either that, or a Kilkenny at a pub (I later switched to Guinness for my simple pub beer). Anyway, what really got me interested was the Czech lager. But then I discovered the great "Beer corner" of my nearest town (Göteborg/Gothenburg), where there's several pubs every block. One of them was "Haket" ("The joint"), which was a pub specializing in having hundreds of beer sorts. And well, that's where I ended up.