A variety of tools cut Plexiglas well, including a circular saw, a jigsaw, a router or a scoring knife. The most precise way is using a laser machine. The choice depends on the thickness of the material, the shape of the cut and the budget.
The cheapest tool for cutting Plexiglas is the scoring knife. It's most suitable for thin pieces of Plexiglas. The circular saw is good for making a straight cut. It's better to use a saw with a fine blade with closely spaced teeth, with a rake angle of zero degrees.
A jigsaw with a blade with reduced depth is good for making a curved cut. Use of light lubricant oil prevents melting of the Plexiglas. A router can cut both a straight or a curved edge. A sharp, slow-spiral bit is a good choice for work with Plexiglas.