Firstly, Battlefront 3 is something I require greatly, and a new Jedi Knight game would be GREAT - Jedi Academy was really well done, and even had surprisingly fun multiplayer, and I'd love to see where they'd take Kyle Katarn and Jaden in a new game.
But my all time favorite LucasArts Game That Nobody Ever Remembers?
MORTIMER AND THE RIDDLE OF THE MEDALLION.
It was this on-rails educational shooter where you piloted a giant freakin' snail who flew around various environments and you used his slime to shoot animals that had all been turned to stone by the evil Lazlo, punctuated by "boss fights" that were really well done animal quizzes with fun songs. The tagline of the game was "Fly The Slimy Skies". And it was GREAT.
Making good educational games that are still educational but also fun is exceedingly difficult, and Mortimer (along with the Magic School Bus series) was the best there was. Jump Start was good, but the minigames became repetitive, and the Math Blaster franchise only really picked up in gameplay variety until right before it was terminated. And of course there are all the uniformly excellent MECC games, but that's a different story.
Point is, a reboot of Mortimer with more environments/stages, greater diversity of animals, and more cheesy but great songs would be amazing. While I'm dreaming, can we have a new Number Munchers game?