This might be a fun thread, so I might as well give it a go.
Mention games that have name conflicts.
For example: Polaris.
The first time someone brought up that he wanted to try Polaris with me I was totally thrilled because I never thought I would meet an American role player that spoke enough French that he would have read this French JDR about people living under the sea after an apocalypse that has rendered the skies dangerous to be exposed to.
But no. He wanted to play Ben Lehman's game of Chivalric Tragedy, which once I learned what it was, was kind of cool in itself.
Ooh, another example: d20.
This also caught me off guard because I'd stopped playing Dungeons and Dragons, but I did play Traveller, so I was familiar with the d20 system, it was the system that TNE uses. So someone asked me, if I knew how to play d20 and I start asking him if he was putting together a Traveller game or Dark Conspiracy or Twilight 2000, and he looked at me like I was old, which was of course the case.
And then, miraculously, an edition of Traveller came out that used the new d20 system and they called it T20.
Does anyone have any other examples?
It can be games that other people have written or you can bring up games that you wrote and wanted to give a certain title, but some publisher beat you to it.