Here is an idea that I have used a lot over the years. Create your own grid based on input from a variety of functional areas within your organization. Then give each person, 5 colored stickers and the color simply represents their department and not them individually.
Ask them to place their colored stickers on the square(s) of their own choosing. They don’t have to pick their own department square and they can put all of their stickers on one square if they want.
Find the squares with the most stickers and do the top 5. Here is a hint. The best square to work on should have the most colors. Any square with very few stickers should be dropped.