Tools differ from person to person, my favorites could be completely from other designers. Even in the same team, designers are using different tools to achieve the result.
UX design process is divided into many stages; research, brainstorming, wireframing, prototyping, user testing, production, and much more. Each stage requires its own set of tools for making sure the delivered output is excellent. Here are some of my favorite tools.
Killer Design Tools to Enhance the Scope of User Experience