These days, usually just boxer briefs and only moderately 'revealing' trousers.
One of my suits, though, is somehow cut in such a way that unless I am careful (e.g., remember to wear briefs), its trousers can, and sometimes do, show a great deal.
Also, back in college, I had this pair of old white jeans that was fairly tight and whose cloth was no longer at all stiff. Needless to say, it pretty much showed everything, but not in a 'blatant' way (not like I was wearing leather pants or anything). I was usually too self conscious to wear them. But every so often I'd haul them out and wear them around, though usually not anywhere where I'd run into a lot of people I knew.
One time, when I was visiting NYC, I was feeling especially adventurous and horny, so I decided to try making myself out as 'bait' and see what would happen.
So, I put on these same jeans, plus a sweatshirt from my college (a pretty prestigious one, not from NYC), and also brought along a book of poems and a tourist map. Then I started riding the subway, poring over the map, looking a little 'lost,' etc. Well, for all that effort, I did end up getting a fair number of looks and winks (but mostly from guys). A few cute girls did strike up conversations, which I thought was hot, but unfortunately no hookups or anything came of it. But it was an exciting little adventure nevertheless.
