Geist
You play as a ghost, and you possess things to solve puzzles and kill guards, it's fucking amazing
Already said was Psychonauts, and honestly, Dante's Inferno deserves a sequel, if anything, to see how it gets promo'd.
Sly Cooper 2
Yes, there is a sly Cooper 3, but it doesn't have the same feel as Sly 2. Sly 2 broke up the team at points and was about enormous heists. 3 was about sabotage and recruitment. I want another game where the first 40 minutes of gameplay is sneaking around, planting stuff, spying on the targets, building a plan, then executing it and beating a disco lizard with what can basically called a Pimp cane. 3 was about 1 heist, and it was good, but I liked 2 best and want to see mini giant heists