Here's a list of the ones I am still playing or have played and could remember.
This list is mostly Ren'Py and RPG, but there were a couple HTML and others that I felt were decent.
Every game on this list has gender bender in some form: either the MC changes or his friend changes, or he changes others around him...maybe he changes early in the game and you spend the game trying to change him back, or maybe he only gets changed periodically, somewhere in the middle of the story, but gets changed back quickly. Either way...these are, in my opinion, some of the best I've found. Maybe we can keep this list updated....an actual list of Gender Bender games that are mostly Ren'Py and RPG and have actual renders and aren't just text based and not using real porn images.
18Titans
Alenja's Adventures (may or may not count...female temporarily gets a dick...but to me, that is still gender bender lol)
Cellular Shift
Chemical Change
Chemical Change Act 2
Chemical Regression
Chemical Travel
Chemically Solvent
Dominant Witches
Earn Your Freedom
Earn Your Freedom 3D
Exchange
Fanucci's Amazing Pizza
Full Service Shop
Healslut
High Jinx
Interns Of Ecstasy Island
Lab Rats
Lab Rats 2
Love Change
Lunars Chosen
Of Birds And Bees
Pact With A Witch
re: Dreamer
SexBot (may or may not count...female temporarily gets a dick...but to me, that is still gender bender lol)
Shattered
Sissy Dream
SlaveGirls Rising (tagged abandoned but it isn't. have to check tfgames regularly..fans also try to update the F95 thread when updates show up)
SpaceCorps XXX
Student Transfer
Succubus Contract
Succubus Contract II
Summer Of Shame
The Fixer
The Proteus Effect
The Vampire's Curse
Transwitch
Unyielding