Security- No matter how bad the economy is there will always be a need for policemen, fireman, etc.
Health care- Once again it does not matter how bad the times are we will constantly need highly trained nurses, doctors, physical therapists, etc.
Education- The economy may be going downhill, but the population isn't. This only means teachers and principals will almost never lose their jobs in poor times.
Food Industry- No one can go without eating even during the recession. People will start going to cheaper take-away restaurants, rather than all the highly priced restaurants that will probably fall during these times.
Handyman Services- This varies from electricians to carpenters, even to automobile mechanics. Skilled professionals in these so called "trades" will still need to make emergency repairs.