I'll start but what are yours?
Could pretty much list my whole collection...
Things I almost definitely won't play again, but have played and worthy of mention.
Shadowrun 1st Ed to 4th - Rules got progressively more complex with each edition, just not the sort of thing I'd like to play, rather play a real cyberpunk game. Played every weekend for several years so it takes up so much shelf space.
Weapons of the Gods - Really love the mechanics of this game, but it is very lore heavy for both the players and the GM, don't think I will find folks willing to invest the time in learning the lore.
Duty and Honour - Sharpe Rifles the RPG, not sure the setting suits modern gamers sensibilities.
Champions - Or Hero System in general, don't think I would play or persuade other to play a game this complex anymore.
Birthright for 2nd Ed AD&D - Easily the most interesting setting for the game, not sure 2nd Ed were everyone is human is likely to be a popular campaign suggestion.
Flashing Blades / En Garde! - Sexism of the historical period makes it less appealing, see Duty and Honour.
Star Wars (any edition, and I have far to many editions) - Disney have made me loose all interest in the franchise.
The list goes on and on, Alternity, MERP, etc. Most of the ones I mention above I have fond memories of, but just are really unlikely to hit the table again even though I kind of would like them too. Now one I will never play again out of a real dislike...
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Things I haven't played and suspect I never will (but would like to. It will only get played if I run it and I would rather be a player)
The Expanse - Suffers from same issue as Star Wars, and other licenses, the main characters in the original media already did the most exciting/important stuff.
Buffy the Vampire Slayer - Same reason as above.
Don't Rest Your Head - Insomniacs in a mad world, interesting dice mechanic and concept, but of a difficult setting to grasp and run for a group.
Underground - Ex Military Super Heroes returning to a civilian life that rejects them.
Millennium's End - Too complex but great source material for anything modern.
James Bond 007 - Got the set, it's really nice to look at but a RPG that's really about a lone agent? I just don't see it working for group play.
There are several more but these are the ones I'm most disappointed about not playing.
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Weirder games I want to get to the table but haven't yet (but will even if I am the one forced to run it)
Zombicide Chronicles - the RPG of the Board game. Want to see how the adrenaline mechanic works in play.
Conspiracy X - The original edition, with Zener cards for psychic powers, and building your own cell.
Dread - Jenga horror game, need the right players and it is not my current group.
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If I had the choice to never play again... (somewhat joking here)
Pathfinder and/or D&D - God I hate high magic heroic fantasy, particularly with classes and levels. Its what my current group prefers.