U-shank jigsaw blades (get type appropriate to your material)

Jig saws can cut wood, plastic, and some types of metal. They are typically used to cut interior cuts (holes) in workpieces and curved cuts. They can cut larger pieces of wood than either the bandsaw or scrollsaw, which are limited by their throat depths.

Jig saws have a tendency to produce blowout on the underside of the workpiece, and often produce unintentionally angled cuts. To reduce this, choose a blade appropriate to your material, operate the jigsaw at the correct speed for the material (wood: fast, metal: slow), ensure the base is at 90 degrees to the blade, use a sharp blade, and don't push the saw forward too quickly. It may also be advisable to run masking tape over the bottom of the workpiece to reduce blowout.

When making interior cuts, wait for the jigsaw to stop completely before removing it from the workpiece. Failure to do so will result in bent or broken blades and dents in the workpiece.

The manual for this jigsaw, which includes directions on changing blades, is here.