Your interviewer wants to know how familiar you are with the industry's applications. They also want to know if you intentionally stay up-to-date on new programs, tools, and product developments.
You can list the most popular tools you currently work with or have worked with in the past, and mention whether you have worked on proprietary systems. Mention any skills with less common programs that are in demand.
Avoid mentioning programs that you haven't worked with for 3-5 years, or any system you aren't comfortable enough to have a user-level technical discussion about. Also, don't mention proprietary systems by name unless they were built on a well-known framework where your knowledge could transfer.
