Best game to have never had a sequel/remake/spinoff/spiritual successor?

[Kaunisto]

agree on Grim Fandango and Conker's Bad Fur Day

also:

XIII (a basic shooter, but the celshading and comics stuff is cool and it ends on huge cliffhanger)
Dragon Strike (gold box D&D game, the best dragon flight sim ever)
Live a Live (SNes JRPG)