I've player Tunnels & Trolls solo adventures with characters from Monsters! Monsters!, and hacked En Garde!, watched in wonder as people actually claimed to play first edition Chivalry and Sorcery (still love the material as a sourcebook, although it's bloody hard to read), laughed myself silly at the creatures in Star Patrol, expressed disdain at Superhero 2044, and was sorely disappointed with Arduin Adventure. I encourage use of Swordbearer at numerous opportunities.
But where oh where, can I even find a seventh generation poorly scanned copy of Realm of Yolmi, Spawn of Fashan, or even All-Adventure Action Roleplay Game!?
The quest goes on in strange online stores, forgotten bookstores, and even opportunity shops. It's gaming archaeology for hidden ancient treasures.