The first Psychonauts is a true Tim Schafer game: unconventional and a bit absurd, but funny and entertaining nonetheless. And make no mistake, this game is old, as is obvious by the graphics and certain game designs. And while the art style is unique, is grotesqueness is also not for everybody, sure. But I first played it a few years ago and so can say: even without nostalgia googles, it is a fun collectathon in today's age, if you can forgive some old school jank.
You play as Raz, a kid with psychic abilities that sneaks into a training camp for psychic secret agents, the titular Psychonauts. He wants to be one as well, but his family of circus artists forbid it. Psychonauts can enter the minds of other people and can access memories or help with psychical problems in this way. And the mind levels of all the different characters are the highlight of the game. Every single mindscape is unique for each character with different objectives and mechanics. You have one mind stuck in a 70s disco party, where you mostly have to use a bouncing ball to float around. One from a small guy with Napoleon complex, where everything is set up like a wargame or another from a failed actress where you have to literally set the stage and tell her life story and thereby help her come to term with it.
If you like unconventional designs, collectathons and can forgive some old school control and game design issues & somehow haven't played this game yet, I highly recommend it! The creativity in its characters and their mind levels is pretty unique. The sequel Psychonauts 2 is also a great game and modernise the formula without losing it's charm. Between those two games is also a plot relevant VR game "Psychonauts in the Rhombus of Ruin". It is a fun little VR game, but if you can't play it, just watch a let's play or read a story summary, it's not a long game and only the setup for the beginning of the second main game.
It's available on GoG & Steam.