- I've never played or run Call of Cthulu. I've read a ton of Lovecraft, I owned 5th edition CoC for several years, and I think it would be fun to play in a limited campaign (like my star wars runs) but I never have. Even though it's considered one of the classics, my players never wanted to play it and no one around here ever wanted to run it.
- I've never owned, played, or run any of White Wolf's World of Darkness games - no Vampire, no Werewolf, no Mage/Mummy/Hunter etc. I know they were popular but not with the guys I ran with.
- At one time or another I owned Midnight, Oriental Adventures, Dragonlance, Dawnforge, and Eberron for 3rd edition but I never played or ran any of them. I picked them up at various discounts and assumed at some point we would try them out (we played a lot of d20) but we never did.
- I own all of the published game books for 1st, 2nd, and 3rd edition Shadowrun but not a single 4th edition book. They just changed it too much and my players stopped caring. I could run for years with the material I have, so the incentive to rush out and buy a new version I like less is just not there.
- I own almost everything for Deadlands, all of Deadlands d20, GURPS Deadlands, and 2 copies of Deadlands Reloaded for Savage Worlds but I've never run a game of it. We have come close several times but it never has worked out.
- I have a full set of the Decipher Star Trek rulebooks and have never played or run it. I loved Fasa Trek and have a ton of stuff for it but I played it a lot too. When Last Unicorn's version came out I thought it was terrible. Then Decipher came out with a new version and it's pretty good. The only problem is my players seem totally uninterested in Trek, old or new, klingons or feds, it doesn't matter.
- Babylon 5 - It's the only TV show I own a full set of on DVD, still in my opinion the flagship for knowing what you are doing with your story and your characters when you set out enabling you to work in long-term plots and character arcs (I'm looking at you X-Files and Lost) and come to a solid climax. I picked up every damn book for the d20 version (both 1st and 2nd edition), the deckplans, 3 different miniatures rules for it plus some miniatures and my players just have had no interest in it at all. I have campaign ideas written out, adventure notes, long term plots I could work in - none of it matters, I've never run a single session of it. I finally dumped the whole set not too long ago because I was tired of the space it was taking - and probably a little frustration was in there too. I think if I ever did get to run it I would just go Savage Worlds or Traveller (Mongoose put out a pair of books for this) and maybe use the miniature rules for space combat (I kept those) and not sweat it, rather than keeping 3 feet of bookshelf tied up in d20 minutia.
Anyway, there are the major gaps in my RPG background. Some of the are hard to believe considering I've played multiple sessions of Timeship and have run 2 Rifts campaigns, but there you go.