There are a lot of tools out there to help both user experience and user interface designers do their work. Here is a list of my favorite design tools in no particular order.
Adobe Photoshop–In addition to resizing and touching up photography to use on websites, I also use Adobe Photoshop for visual mock-ups. A popular (and much more inexpensive option) is Affinity Designer.
Adobe Illustrator–I don't use Adobe Illustrator often in UX/UI design, but it's my go-to program if I need to create custom iconography for a website or mobile app. Affinity Designer is also an alternative for Illustrator.
Adobe InDesign–While Adobe InDesign is typically used to design print pieces like brochures and postcards, I find it a great way to do quick wireframes and sitemaps. Other popular wireframing tools are Balsamiq, Microsoft Visio, and Omnigraffle.
Adobe XD–Adobe XD originally started off as a prototyping software, but it's constantly updated and it can be used for many steps of the design process including wireframes, visual mock-ups, and prototypes. Other popular prototyping tools are Sketch, InVision, and Figma.
Axure–Axure, like Adobe XD, can be used for wireframing and prototyping, but it can also be used to create user journey maps, sitemaps, and other diagrams.
Sonix–Sonix turns audio files into typed transcripts. I use it to transcript my user interview audio files. It's not perfect, but it saves a ton of time.
Post-it Notes–Post-it Notes are the little darling of user experience designers everywhere. Search "UX" on a stock photography site and most likely you'll be presented with lots of images of designers using Post-it Notes. Post-its are great for brainstorming, affinity mapping, and more.
Paper & Pencil–Good old paper and pencil is a very useful tool in the design process. I often start wireframes on paper to get out a lot of rough ideas fast.