With persistence and a little bit of luck, almost any type of vehicle can be hitchhiked. They, however, vary in difficulty, comfort, and availability.
These are very basic road based transports. These are very prevalent in the first and second worlds, not so much in the third. The only obstacles to getting a ride on them are them being full (definitions of full may vary) or the driver not wanting/being afraid to take you.
It seems possible for one person to hitchhike a motorcycle by sitting behind the driver. This likely requires a helmet for safety reasons.
This is another road-based transport, significantly slower than cars. They exist anywhere cargo needs to be moved and only have a few empty seats, although the driver rarely has company. An obstacle that applies to trucks is insurance.
Busses, Minibusses, Commercial Vans, Marshrutkas (CIS)
Not easy to hitchhike, as the whole point of these road-based transports is to make money. If they took people for free, they could not do that. This is not to say it is not possible, if you look miserable enough the driver may pity you. It may be possible to sneak into large busses through a rear door if there is one.
While freight hopping is generally illegal and universally dangerous, it may be possible that the operator takes you. Crossing borders complicates things.
Similar to bus+, but with more possibilities to bend the rules for creative people.
These are rarely used to go very far, but hitchhiking them will surely make for an interesting story later.
Frequently used for short trips instead of airplanes as they are easier to maneuver but are not effective for going far.
Largely a thing of the past, please share any hitchhiking experience if you have it.
Hot Air Baloon
The most basic of all air transports, these are used by hobbyists around the world but rarely as transports.
The slowest of all transports, people have been using animals to get around for hundreds of thousands of years. The animal you encounter is most likely to be determined by your climate zone.
The most popular animal transport around the world.
Especially popular in Central and South Asia, and to a lesser degree Greater Persia and the Caucasus. Possible to find elsewhere, though much harder than the horse.
The Offspring of a horse and a donkey. See above.
Popular in the Arctic, these animals are resistant to the cold and very energetic, but comparatively weak, so large amounts of them are needed.
Popular throughout Asia and North Africa, this animal can survive on the little water available in the desert.
Wild yaks roam Tibet, Nepal, and India. Domesticated yaks also exist in Central Asia, Xinjiang, and Mongolia. Yaks cannot survive in low altitudes due to their thick coats.
Popular throughout South and Southeast Asia.
Can it be ridden? It is big and strong, sure, but not generally known to drive people Let us know.
While they are glad to please you when you visit them at an aquarium, please do not ride dolphins in the wild, both for their sake and yours.
Please share what transports you have had with hitchhiking various transports.