Let's see...
Inadvertently climbed Katahdin without any food, which my dad and I somehow left behind in the car. We did have water, though...oh, and my dad thought it'd be a good idea to climb the mountain in a dress shirt and polyester pants. I chewed him out pretty good for that one, and he never did so on a hike again. Apparently some guys who passed us on the way up made a bet on whether we'd reach the top (we did).
We climbed up the Thunderbolt Ski trail on Greylock in December, with only about 3 hours of daylight left when we started out. We had no equipment beyond some water and a map, and I almost didn't even bring hat or gloves "because it wasn't that cold out". Several dangerous snowy slopes and treacherous icy patches, and one summit, later, we were nearly back at the car, but nearly out of daylight. And then we ran into a hiker even worse off than we were! He was apparently miles from where he needed to be, and after looking at our map took off; hopefully he made it.
Spruce Knob, also in winter. The plan was, the gate probably being closed, my dad and I would walk the ~20 miles roundtrip to the top, mostly in the dark. We had two flashlights, each with maybe 2 1/2 hours of light to them. Very luckily for us, the gate happened to be open, but we still had a nice treacherous drive most of the way up in my dad's Geo Metro, nearly sliding off the road onto the steep mountainside once or twice. Again, we somehow made the top and lived to tell the tale.
In my defense, I was no older than 14 for any of this