Pokemon fighting game Pokken Tournament DX is currently free to try on Nintendo Switch.
The free trial will be available until Tuesday, August 4, but you'll need an active Nintendo Switch Online subscription to access it – not just to play it online, but to get the demo at all. And while you won't be able to keep playing the game once the trial ends, if you like what you play, you'll be able to get it for 30% off until August 11. Like most Nintendo games (well, technically a Bandai game), Pokken Tournament DX doesn't go on sale terribly often, so this is also a good period to buy it outright if you've been waiting for a discount.
It looks like the free trial is basically just the full game, which is generally how these Nintendo Switch Online freebies work. If you do decide to buy the game, your progress from the trial will carry over.
Pokken Tournament was initially a Wii U game, and the DX version released on Switch improved on the original in every conceivable way. It looks and runs better, for one, and it starts you off with five new characters, as well as the previously unlockable Mewtwo and Shadow Mewtwo. It's definitely one of the weirder Pokemon spin-offs, but as an arena fighting game, it's a fun and flashy experience that makes for great co-op (and, anecdotally, some of the smoothest online play on Switch, though your mileage may vary). If you have even a passing interest in fighting games, or if you're a die-hard Pokemon fan, it's definitely worth giving the free trial a play.
Speaking of Pokemon spin-offs: let's not forget that New Pokemon Snap has evolved from pipe dream to actual title.