There is a definite need for BOTH scissers and Xacto blades. You may use both on the same material, depending on whether you are cutting a straight line or a curve. The micropunch made the biggest difference in working with PET plastic (soda bottles). It easily makes a hole perfectly sized for florist and beading wire--key for making flowers from individual petals. For making the stem hole in the center of PET flowers I alternate between the Dremel and the woodburning tool, both safer than trying brute force with an Xacto blade.
Some folks use a candle to shape PET plastic, but I greatly prefer a heat gun--it's a much hotter version of a blow dryer, often used for stripping paint. I like that it has a base that is stable for hands-free operation (blowing straight up). The pliers are necessary for holding pieces being heated (did I mention this is REALLY hot?). This heat gun has two settings. Note that if you heat the plastic too long, it will start to foam and turn opaque. Pliers are also essential for stripping the "petals" off of pine cones.
Hot glue is the fastest method of attaching items together, but it does not work well with plastics (especially PET plastics) and is not very flexible. ModgePodge is great for attching paper or fabirc products and also works as both sealer and glue for autumn leaves. Elmer's takes a while to dry but is flexible and clear. Spray glue is best for laminating layers. Strapping tape is strongest when it is wrapped completely around an object. Same is true for masking tape--it is useful for wrapping wired items to protect against sharp ends. Wire to wire connections can be secured by soldering, wire wrap, or taping joints.
Using paint on absorbent materials like cardboard can be tricky. It's a good idea to test on a small sample. Some paper products will absorb too much and get soggy or just not get full coverage. Sometimes you need to seal the surface with varnish or ModgePodge before painting. Permanent and paint markers work best on PET plastic. It is safe to heat items that have been colored with Sharpies. I have not tried heating items colored with paint markers. Paint markers are more opaque than Sharpies, but will mix with Sharpie colors if overlapped. If you want to use both on a transparent material, put them on opposite sides of the surface. Florist tape is prone to being a bit sticky and for having the ends peeling up--a quick fix is to apply sealant to the taped areas.