To have a fun time, Pandemic requires some cheap an unique props. They are very easy to set up, and require minimal investment.
Bolts, (preferably ½ in bolts) and nuts
Mechanics/engineers repair/weld objects by removing/adding bolts to objects. The easiest way to achieve this is by adding doors to your buildings, and putting a small wooden box over the lock. The box would be closed with a number of metal bolts. The engineer player would remove these bolts so players may gain access to the locking mechanism. These boxes can be placed on anything, (around a gas powered generator for example).
If you have stand-alone refs, you can also put a piece of metal near the prop, and have the mechanic player hit it with a hammer for a set amount of time, (ref would keep a stop-watch). This would be the act of “repairing” the prop.
Placing combination locks on props/doors allows hacker players to gather data from computers. This also allows players to “bribe” mercs for combinations.
Old/cheap used computers
These require power, but you can find free old computers pretty much anywhere. Hook them up, and have players mine data off of them. If you don't include the operating system on the hard drive, hacker players can carry a thumb drive with a flash copy of windows. This makes them only accessible to hackers.
Portable power is always a great prop. These can be used to power computers, lights, etc.
Military surplus boxes.
These can be placed in various spots so players can search for food/medicine