WORKPRO Premium Utility Knife, Retractable All Metal Heavy Duty Box Cutter, Quick Change Blade Razor Knife, with 10 Extra Blades

Agreed, (a standard utility knife is plenty robust enough, as long as it's got a new blade in it), but I'd recommend getting the X-acto anyway for finer control. I use my X-acto for anything 5-6oz or thinner; it's very precise, cuts cleanly, and is easy for a beginner to handle. Bearing down on the blade is bad for control, and more dangerous because it causes slippage. You don't really need to bear down on a blade if it's sharp enough, and an X-acto with a fresh blade is about as sharp as you can get.