I was recently surprised by the reply, when I asked a 12 year old boy what a Carpenter did. It was a somewhat tentative and questioning, but never the less genuine "Do they lay carpet?"  After that I wasn't game enough to ask what a Plumber did.

Start a conversation with your class about what sort of job they would like to do when they start working.  Suggest that there are thousands of different jobs that people do and ask for unusual jobs that they can think of.  Write the occupation and a brief description of the job or the board.
Next pick a letter and ask the class for an occupation that starts with the letter. 
Z is a great letter Zoo Keeper  and don't forget Zoologists.  According to my Google search there are 60 zoologists working in Western Australia alone, 60% of them work in Perth.  Their salary ranges from $35,000 to $80,000 a year. 
Then offer the following occupations and (by offering clues when you need to) get a description of them from the class to write on the board.

Construction Shotfirer:- Shotfirers assemble, position and detonate explosives to break or dislodge rock and soil or to demolish structures. Learning Areas:- Chemistry, Geography, Mathematics, Physics, Rural Studies.
Maitre d':-Waiters serve food and drinks to guests in hotels, restaurants, clubs and similar establishments.
Gaffer:- Lighting operators position, set up and operate lighting equipment to light sets or studios during stage performances, television broadcasts or film productions. Lighting operators are responsible, both creatively and technically, for lighting interior and outside scenes and must achieve the desired effects through the placement, intensity and colour of lighting.
Palaeontologist:- they study extinct organisms usually in fossils.
Groom:-  Stable hands assist with maintaining and cleaning stables and handling horses    (Stable hand)
And my absolute favourite a 
Cant Gang Sawyer:-  Wood or paper processing machine operators operate sawing and other machines to make logs or cut them into poles or timber pieces; machinery such as rollers and presses to make plywood, particleboard, solid laminate or similar timber products; or papermaking machines, wastepaper pulping machines, driers and cutters to make paper packaging and other products from paper and fibreboard stock.
Chocolatier:  Mix sweeteners and other ingredients, and shape and cook confectionery including chocolate, toffee and other lollies.

This website has a great list of Jobs http://www.myfuture.edu.au/services/default.asp?FunctionID=5010&Action=List&Letter=A  . It is an Australian website and has 30 occupations listed under the letter V, 9 listed under the letter U, and a whooping 216 listed under A.
The site lists everything from Tissue Culture Technician to Waste Collector, gives a description of what the job is, indicates salary range and qualifications needed and related fields of work.