The Tongass National Forest, located solely in Alaska, is the largest national forest in the United States. The best way to see the forest is to drive through it, and I would recommend taking a Yamaha Rhino.
Through the Holland America Cruise line I booked the Alaska 4×4 Nature Safari excursion tour in Sitka, Alaska. I was worrying the entire time leading up to the excursion about being able to control the 4×4, especially if the roads were narrow and the terrain was rough. However, the roads are well defined, and the dips and bumps in the road made it more exciting rather than terrifying. If you are looking for an off-road experience than this might be too tame for you.
We were really lucky with the weather in Sitka, as it did not rain the entire time we were there. The roads were damp, which meant there was not any dust being kicked up, but they were not muddy. The vehicle has a windshield in front, but it is open on the sides so I would dress appropriately just in case you do get muddy.
The excursion takes place on an island in Sitka, so we first took a small enclosed boat ride(and spotted otters along the way). After the twenty minute boat ride, we were given helmets, bear repellent, and shown how to drive the vehicles. The tour lasts about two hours as you drive into the forest and then drive back the way you came. The highlight of the trip was when we spotted a curious bear cub that walked up towards us(luckily without a mama bear in sight).