While most people focus on the things that should be bought in bulk to use in a barter economy those stocks, no matter how vast, will eventually be depleted. Instead, focus on skills you can develop that will be valuable to a world reliant on barter.

Midwife

Anyone trained to assist in natural childbirth and who has the medical skills and experience to do so with limited medical resources is going to be in high demand in the event of a natural disaster or social unrest.

Paramedic

Any first responder is going to be an asset to a community that has limited medical resources. They are trained to deal with emergency situations and medical traumas with limited equipment.

Nurse

Nurses of any level have the basic training necessary to handle most emergency situations and standard medical issues. They are usually the people who identify issues for physicians in a normal situation and this diagnostic skill will be quite valuable.

Veterinarian

Veterinarians and those trained as vet assistants have many of the skills necessary to treat human patients as well. The medications and tools they have can typically be modified to work on humans when necessary and their original training can become invaluable if livestock becomes more of a necessity than a hobby.

Farming

Farming is quite different from gardening. People who have a hobby garden tend to rely heavily on prepackaged solutions to common gardening problems or on specialty seeds for exotic produce. A farmer knows more about the natural rhythms of the land and will be able to find solutions to common problems.

Chemist

A trained chemist will be able to make fuel, medications, alcohol, herbicides, fertilizer, pesticides, explosives, and narcotics. Once these items become difficult to obtain through existing supplies those that can create them with more abundant resources will be in high demand.

Escapism

A skill that allows people to escape from their current reality will be invaluable to a society that has radically changed. A person able to offer entertainment in the form of music, plays, literature, alcohol or drugs is always going to be in demand.

Teaching

Individuals who are able to teach, discipline, and responsibly and effectively monitor children will find their skills in high demand after the initial crisis is over.

Beekeeping

Bees offer a source of calories that are popular and shelf stable for long periods of time. They also improve garden performance. Fuel

The ability to create high quality charcoal to be used as a source of fuel or access to an abundant supply of wood that you can process and distribute will be in high demand as gas for generators and vehicles become less available.

Water Purification

The ability to purify water may be the most valuable skill a person can learn. When pressurized water and standard chlorination efforts are no longer available instances of numerous diseases will begin to reemerge in epidemic proportions. The more methods you know how to use to purify water the better.

Mechanic

Specifically those with the ability to repair and maintain small engines such as those found in generators and how to modify them to run on alternate power sources.

Plumbing

The ability to make water pumps work and to make the transfer of fluid via tubing in unorthodox settings will be invaluable in making new shelters viable and keeping existing structures supplied with water.

Animal Husbandry

The skills and knowledge associated with increasing the instances of successfully breeding healthy offspring from available livestock.

Blade Sharpening

All blades must be sharpened. The right angle and optimal edge created by sacrificing the least amount of metal is not only a skill but also an art form. A true expert will ensure these survival weapons are as sharp as possible and are cared for in a way to make them last as long possible.

Clergy

After a natural disaster or during periods of social unrest people often turn to their faith. Having the ability to discuss and teach people about the faith is always in high demand.

Psychology

A deep understanding of psychology will be invaluable after a crisis. Grief counseling, negotiations, creating new social guidelines, dealing with people going through withdrawal or post-traumatic stress disorder all require special training.

Textiles

Individual who can make cloth from wool or cotton will be able to replace material as it wears out. Those who can design and sew clothing will be able to set themselves up as a tailors to make or repair items as they wear out from constant use.

Martial Arts

The ability to offer people self-defense training of any sort will become more popular as law enforcement breaks down.

Brewmaster

No matter what happens, people will always have a vice that will need a fix. Beer is the third most consumed beverage in the world and also happens to be one of the most common addictions. If you have the skill and ability to brew your own beer, imagine just how valuable you will be after the liquor stores are all boarded up. Just how much would a 6 pack of your home brew be worth?