We were  night hiking into Sheridan Lake in Yellowstone without flashlights and no moon. Nearly walked into the side of a moose who was standing in the trail. Don't know who was more scared. When we got to our car around 4pm the ranger told us that we didn't have a permit to camp, but we weren't camping. Then my buddy told the ranger that we had plenty of light, cuz the snow soaked up the light during the day and let it off slowly through the night. Unamused.

I was driving on Wawona Road southbound turning left onto Glacier Point Road (Chinquapin Junction) in Yosemite during a February. I was heading to Badger Pass to go snowshoeing. The roads were covered with snow, and it was R2 chain conditions with a park ranger manning a checkpoint in Yosemite Valley. I had chains in my trunk, but didn't have to put them on because I was driving an AWD Subaru.

I took the turn a little bit too fast, and did an understeer skid out, where I plowed into a snow bank that was created by plowed snow. That is an interesting intersection, with plenty of extra space all around. Here's what the intersection looks like. Nothing was damaged, but I could imagine a similar turn on one of the areas with sharp drop-offs.

http://maps.google.com/maps?q=Glacier+Point+Road,+Yosemite+National+Park...

I joked with the ranger leading a snowshoe walk that I took out a snow bank on the way over, and he joked back that he might just need to fine me for "damaging federal property".

Caught in a lightning storm, doing the Sage Creek Wilderness Loop in Badlands NP.
 
Very narrowly escaped a bison stampede in Theodore Roosevelt's North Unit.  (One of my best moments.)

Pneumonia in the backcountry of Yellowstone.  I thought it was just a cold...

My dad and I spent a weekend camping in the Shenandoah's just before I left for my tour over in Korea. 
We were quite lucky both that the black bear who decided to enter our tent was more curious than truly hungry, and also that my flashlight in his eyes was enough to startle and frighten him away. 
A pup tent is small for two men; it is microscopic for two men and a bear.

My wife and I were day hiking in the Many Glacier Lodge area of GNP and decided to hike out to Grinnel Glacier Lake.  The hike went well, we arrived at the lake and we were the only ones there.  We decided to have some lunch as we enjoyed the day and the views and we were mostly done when a group of 8 to 10 other day hikers arrived; they also pulled out their lunches.  I grew uncomfortable with the amount of food present, and suggested to my wife that it was time to leave.  She was okay with that but had overheard the other hikers talking about a privy just a short walk back the trail and she wanted to visit it before we continued.  As she headed out ahead of me I remembered seeing the privy as we hiked in and I corrected her course and and headed towards the direction I remembered seeing the privy....only to immediately catch the sight of a grizzly bear sniffing the ground and headed our way!  Of course my heart jumped into my throat and I first yelled "Bear" and then quickly turned to run; only to be quickly stopped by my wife who had by now caught up to me.  My wife warned me that we weren't supposed to run so I quickly turned again to see where the bear was and I continued to yell "Bear".  As I turned around to check on the bear's whereabouts I saw him stand on his hind legs, take a good look at us and then turn and dash off in the opposite direction!  Fortunately the bear was as afraid of us as we were of it and all was well.  Of course the "opposite direction" from where we were was the direction we now needed to hike out, so we had an anxiety filled return hike to Many Glacier Lodge where we saw three more bear, now from the safety of our car, as we departed from the Lodge on our return trip.

Last summer while hiking the Gunsight Pass Trail we had an encounter with a bear. We were near the side trail to Florence Falls when my wife shouted out "hey bear", just as we had been doing every couple of minutes or so. Less than 30 seconds later, and maybe only 20 feet up the trail from us, we heard a loud crashing noise through the undergrowth as a bear scattered out of our way. Although we couldn't see the animal, we assumed it was a bear because of how loud it was, plus we would've been able to see if it was a moose, elk or deer. Either way, it scared the you know what out us.

Jeff
HikinginGlacier.com

Several years ago we were truck camping on the beach at Assateague Island National Seashore in the early fall when the NOAA weather announced a strong tropical storm was approaching from the south. We packed up and left the beach and headed inland to a little Maryland State Park. The winds began to increase and tree branches and pine cones were raining down on us. The weather radio informed that the storm was veering westward and the conditions would be improving along the Atlantic coast. So we set out to head back to Assateague planning to pass  the night in the NPS campground. Driving over the bridge from the mainland was like going to windward in a sailing vessel, the winds were increasing. The Ranger looked as us like we were nuts, but when we told him of the change in the forecast, he called the office and they confirmed that the storm was predicted to turn inland before it reached us. We set up our truck camper with  the jacks deployed to level and steady us and put out our slide-out room. The wind continued to increase. There was a nice new popup trailer just beside us and several other various good sized RV's  scattered about. A fellow showed up at the popup I thought he was going to put down the canvas room, he simply got a few things from the inside and left. The wind was now well above gale force, I have a neat little weather station that I can fit on our ladder and the wind indicator was moving up to over 60 mph sustained. The NOAA now said the tropical storm was back on a northerly  course and would pass along the coast line. In a short time the popup completely disintergrated, clothes, mattresses, blankets and lots of other stuff was blown off down wind. We were bouncing around as we did when we were anchored in a storm in our sailing ketch, we pulled in  the slideout, and rode it out.
The storm blew bye in just a few hours, a number of folks came to help us gather up some of our neighbors stuff that had   lodged in the brush. He returned mad as a hornet, did not thank anyone for trying to save some of his property, he blamed the Rangers for not informing   him of the storm.The Ranger later said they had asked him to put the tent down . And when he said he was going  to abandon the wreck in the park, he was informed he would billed on his credit card, with which he'd payed, for the salvage. He complied.
We were lucky we had no damage. as we were somewhat in the lee of a sand dune. One of the Park Volunteers had parked his new truck in an area with a long open fetch across the sand, which blasted the paint from one side. All who were there will remember the howl of the just below hurricane strength winds. Something I learned from many years of sailing in the tropics, I ignored that day, Hurricanes and Tropical Storms do not listen to the radio or TV, they do as they wish!