I've made some free-to-play games about weird sex.
The largest (by far) is Boobjitsu Matriarch, a text-based twine game. You have succeeded your mother as chief of the Megalostithos tribe, and now must protect your people with the power of boobjitsu, the martial art of boob combat. In your quest to keep your people together and safe, you will encounter strange opponents and find mystical items. Unsurprisingly, those mystical items will transform your breasts, shaping your ability to fight with boobjitsu. If you hadn't figured it out, this is a silly game.
Or join the festivities at the Pixiespawn Festival, where grad students of sorcery use magic spells and dirty tricks to transform and impregnate their fellow students. This roguelike browser game features saucy magic, aphrodisiac pixie dust, body transformations, and loads of pregnancies. The enchanted campus is procedurally generated and switches itself around every night during the witching hour. Spell-slinging duels transition into orgies and back again in an unrelenting stream of action sequences. There's something here for the whole family, assuming the whole family are all adults with weird kinks.
Or strive to claim the Throne of the Size Queen in a lusty head-to-head battle royale. You and seven other contestants enter the Tienay Arena. Can you defeat your opponents and steal their boobs, butts, and muscles, or will you lose everything and flee, shapeless and ashamed? Only the winner may claim the throne... and only once their body is big and bouncy and curvy enough to do so.
Or enter a legendary spiritual retreat full of strange customs, games, and transformations in The Cloister of Abundant Communion. Your goal is to penetrate the Cloister's innermost recesses. To get there, you must meet, carouse, and sate a menagerie of colorful characters, all with their own peculiar desires and idiosyncrasies. Every encounter you have changes you: sometimes in ways you want, sometimes in ways you don't. But if you come to the center of the Cloister, a revelatory epiphany awaits you.
Or join the clinical trials at Daisycream Cosmetics and Dairy. This not-at-all sinister corporation of dubious governance and ethics is conducting a round of human testing at their remote dairy ranch, which they've refurbished to welcome test subjects who won't be missed if they suddenly disappear. Room and board, access to the dispensary full of Daisycream cosmetics, and a fully-equipped gym are all included in your generous compensation package!
I've also made a throw-away satire game called Grow Your Boobs, which does what it says on the tin and basically nothing else. It's short and dumb and barely merits mention here.
If you like this sort of thing and would like to see more, consider supporting my Patreon Campaign. Thanks!