An advantage of working with PVC is that you don’t need many tools. However, the first one on the list is a “must have.” for the $10 – $20 it costs, you will do a much nicer job and won’t dread cutting pieces to size.
Any store that sells PVC pipe will sell one or more versions of hand-held pipe cutting tools. What they are is a sharp knife opposite a curved “cradle,” with a ratcheting handle. The knife is driven a small way through the pipe with each squeeze of the handle. I would buy the heaviest-duty one you can easily find if you plan on doing more than a couple of obstacles; my local Ace Hardware had two and the price difference was only $2 between them ($10 and $12, both made overseas and not of “pro” quality). A “pro” quality hand-held cutter will be $50 or more, but quality tools are a wise investment if you’re going to be doing a lot of work.
These aren’t essential, but sometimes when you put together an assembly without glue for a trial fit pipe can get firmly wedged into the connector. A gentle grip with the pliers on the open end of the pipe (inserting one jaw of the pliers inside of the pipe) and a twist while pulling will see the pipe come free.
If you make jumps or work with boards (plastic or wood) you will need a way to cut the material. For PVC, a hacksaw works well, while a normal handsaw or circular saw works well for wood. You can use a fine-tooth blade in a power saw to cut PVC, but the PVC can melt from the heat of cutting–and I wouldn’t use an expensive blade!
You’ll need this to measure lengths of pipe to cut.
For marking pipe and boards for cutting and alignment.