You can currently get both The Stanley Parable and Watch Dogs for free on the Epic Games Store as part of their weekly giveaways.
Watch Dogs isn't nearly as good as it's sequel, but it's worth playing through just to get some lore before playing the second game, which is excellent. It's not terrible, but it lacks some of the charm and personality of the second game, for me. It's still pretty innovative as a gameplay experience, though, and if you like stealth-em-ups, you'll enjoy this.
It was pretty poorly optimised and at the centre of criticism for graphics that didn't live up to the pre-release hype, but with modern hardware, it runs just fine, and there's mods out there to restore some of those bells and whistles.
The Stanley Parable on the other hand is absolutely worth every second of the time you're about to sink into it. It's a first person game, and that's about as far as I can go with it. It's in a genre all of it's own and sees you working torwards multiple different endings and scenarios that all start in your office, wondering where all your co-workers have gone.
These games are both free until the 26th of March.