Whatever I feel like on a given day. I hate itineraries. I like going on vacation with a general idea of what I can do, and then picking and choosing when I get there.
That's difficult to say, because it's entirely dependent on the destination.
I like both urban and scenic exploration. I have trouble sitting around, unless my body needs the rest. So, I stray away from most "leisure" activities. Sitting on the beach for hours is not for me. If the destination has a high walkability factor, I will walk everywhere I physically can, and I will do it A LOT.
I barely take any pictures. I find that they detract from my being in the moment, and they never capture what I hope.
I do like thrifting for niche, often older electronics and peripherals.
I like food.
I like cigars, and love cigar bars, because the atmosphere and activity is excellent for meeting locals and travellers alike. That is one thing I will always scout out and do.
I went to Osaka, Japan earlier this year. I returned with 2 large suitcases packed full of retro video game consoles and peripherals. Their LaserDisc stores were insane and floor to ceiling with stacks of discs. I so badly wanted to pick through them, but LaserDiscs are notoriously heavy, and I couldn't spare the luggage weight.
A few years back I spent a year living on the road, all across the US. I brought back a huge haul that time, notable acquisitions being an Atari Jaguar and an NEC PC Engine.
One of the coolest things I saw in Osaka was a monthly flea market held on the grounds of Shitennoji Temple. It's a pretty big temple so there were a lot of vendors. I spent the better part of the morning eating amazing food and browsing through old games and records, vintage clothes, and all sorts of other old stuff. I ended up getting some old woodworking tools, a couple of wooden serving platters, and a copy of Dragon Quest V.