Design for Excellence (aka Design for X, DFX) is a systematic approach for designing where X is the objective for the product or process
FMEA (Failure Mode Effects Analysis) is a tool that helps us anticipate what might go wrong with a process and identify the possible causes.
Taguchi Robust Design is a function of product design. Robust products have a strong signal-to-noise ratio.
The 5 Whys is a root cause analysis technique used in the Analyze phase of the Six Sigma DMAIC (Define, Measure, Analyze, Improve, Control).
Brainstorming generates a large number of creative ideas in a short period of time. In Six Sigma, it helps you find solutions to issues.