Tag "Portal 3"
How it works
You can tag anything on ModDB on ModDB, and all tags can be voted up/down by the community depending on their relevance.
Official tags, as well as up-voted tags will appear higher in the list as they are deemed the most relevant.
If you discover a page that does not have any tags applied, why not help out the community by submitting tags, or posting a comment with #tags in it, which will be automatically linked.