My friend Alex and I drove from London to Mongolia in a car with a 1L engine as part of The Mongol Rally, a drive to raise money for charity. We drove across Mongolia, entering from Russia and driving eastward until we arrived at Ulaanbaatar. All in, the trip took us 53 days and we visited 20 countries. Here's the gear we couldn't leave without:
We used this stove to cook nearly every meal of the trip. It's easy to use, reliable, and perhaps most importantly, accepts many different types of fuel. We left London with clean-burning white gas, but our supplies quickly ran out. With this stove we could use (less clean-burning) unleaded gasoline which was widely available. The entire system (excluding the fuel bottles) stows into a carry bag that is about half the size of a loaf of bread.
These bags are great for long trips. They are very tough and are water resistant, though not waterproof, and can fit an unbelievable amount of stuff. The only downside of this bag is that its heavy, so I wouldn't recommend it for people who will need to walk while carrying their bag for long distances. For this type of car travel, it was perfect.
I'm now on my third Arc'teryx hard shell jacket since I first bought one in 2005. This jacket (the latest model of the one I have) has become indispensable. It's a lightweight layer you can throw on when it starts raining, snowing, or is just too windy. I've also had amazingly good experiences with Arc'teryx's repairs team. They build the jacket in panels, so you can replace one of the panels without needing to fully replace the jacket. People who are going to be in particularly nasty weather may want to look at the Alpha SV (SV for 'Severe'), but I like the versatility of the Alpha AR.
Typically steel wheels are the budget option, but for remote, mixed terrain drives like the Mongol Rally, they are a must have. The reason? Steel dents where aluminum and other materials break. This means when you hit the mother of all potholes in Turkmenistan, you can just take the wheel off and bang it back into shape with a mallet.
Tabasco makes everything taste better. The days where we ran out of our supply were some of the darkest of the trip. Luckily we found more in Russia. Is it the tastiest or hottest hot sauce? No, but it's there when you need it. According to the description on Amazon each 12oz bottle is "packed with 71 servings of taste bud tantalizing flavor" but I think if you are using it right you'll get about 20-30 servings per.
Seattle based Feathered Friends makes the very best down products. The Swallow is a great example; it's warm, cozy, and roomy enough for a great night sleep. In the morning the bag stuffs down into a tiny stuff sack. If the down fill gets soaking wet it won't stay warm, so you may also want to invest in a bivy sack to keep things dry.
We got lost pretty frequently. When this happened we'd pull over the car and look at a map. A fancy British man who went by PA (for 'Posh Austin') shared a bit of wisdom with us: if you light your pipe while you're looking at the map, you're not lost, you're exploring. This makes no sense to me now, but it was convincing at the time. Good pipe tobacco smells amazing and the nicotine rush helps you stay awake during long drives. Of course, smoking is very bad for you and is habit forming, so think carefully if you want to try this one.
I've got a Peterson of Dublin pipe and get my tobacco from New York's Barclay Rex (on a recommendation from my friend Carlos).