Risk Assessment Tool Homework

If you were tasked with assembling a 'toolkit' using only free or open source tools to perform network security assessment.

(1) What software applications or "tools" would you use? 

(2)What platform (Operating System) would you use? (3)How does this toolkit differ from that you would use for an application security assessment, wireless security assessment?  You can list other types of related assessments if you know if how you might adjust for the given scenario.