Exacto knife / box cutter
Glue (If you like, use gorilla glue. It is stronger, but in the long run it won't make any difference after fiberglassing, but any glue would work. The reason I have chosen this one is just to save money)
A helmet file to be used with pepakura:MK VI
In my opinion, the MK VI is the most difficult, but it is the most popular. If you want simpler models, then just post a comment and I'll give you a link to one!