⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⣀⣤⣀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣰⠟⠉⠀⠙⢷⣄
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣸⠇⠀⠀⠀⠀⠀⠹⣆
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢠⡟⠀⠀⠀⠀⠀⠀⠀⢹⡆
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⣼⣁⣤⣤⡤⠤⠤⠤⢤⣼⣷⣀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢠⡞⠉⠉⠀⢀⣀⣀⣀⣀⡀⠀⠀⠀⠙⢷
⠀⠀⠀⢠⡴⠒⢶⣄⣤⣀⣀⣀⡀⠀⠀⠀⣸⣧⠶⠞⠛⠉⠉⠉⠉⠉⠙⠛⠳⢦⣤⣼⠃⠀⠀⠀⠀⢀⣀⠀⢀⣀⡀
⠀⠀⢠⡟⠀⠀⠀⠉⠉⠙⠉⠉⢻⢀⣤⠞⠋⣁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣀⠀⠈⠙⢷⣄⠀⠀⢰⡟⠙⣿⠟⠉⠻⣆
⠀⣠⠾⢷⡄⠀⠀⠀⠀⠀⠀⠀⣸⡟⠁⠀⢠⠋⢧⡀⠀⠀⠀⠀⠀⠀⠀⣰⠋⢳⡀⠀⠀⠙⣷⡴⠟⠃⠀⠀⠀⠀⢀⣿
⢸⡇⠀⠀⠀⠀⠀⠀⠀⠀⣴⠟⠋⠁⠀⠀⠘⢂⣈⣁⠀⠀⠀⠀⠀⠀⠀⣋⣉⣛⢃⠀⠀⠀⣿⡄⠀⠀⠀⠀⠀⠀⠛⠛⢻⣄
⠸⣧⣀⠀⠀⠀⠀⠀⠀⢠⣿⠀⠀⠀⠀⠀⢾⢻⣷⡟⢳⠀⠀⠀⠀⠀⣼⢻⣿⠟⡟⠀⠀⠀⢹⡷⠀⠀⠀⠀⠀⠀⠀⠀⠀⣿
⠀⢸⡃⠀⠀⠀⠀⠀⠀⠀⢹⣧⠖⠚⠒⢄⠘⢷⣤⡴⠟⣣⡤⠤⣤⣄⠿⢦⣥⡴⢣⠖⠉⠑⢺⡷⣦⡄⠀⠀⠀⠀⢀⣠⡾⠃
⠀⠈⠛⣶⠆⠀⠀⠀⠀⠰⣿⡇⠀⠀⠀⢈⠀⠀⠀⡴⠋⠁⠀⠀⠀⠈⠻⣦⠀⠀⢦⠀⠀⠀⠀⣿⣟⠀⠀⠀⠀⠀⠀⠈⣿
⠀⠀⠀⢻⣄⣠⡀⠀⠀⢀⣾⠙⠦⠤⢤⣮⣤⣄⢰⠁⠀⠀⠀⠀⠀⠀⠀⢸⡆⢀⣈⣶⣤⠤⠊⠀⢹⡇⠀⠀⢀⣀⣠⡴⠟
⠀⠀⠀⠀⠈⠙⠳⠦⠶⠿⣇⠀⠀⠀⡞⣡⠀⠈⠻⡄⠀⠀⠀⠀⠀⠀⠀⢸⡷⠛⢱⣄⠹⡆⠀⠀⠈⣿⠶⠶⠛⠉⠉
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢻⡄⠀⠀⣇⠘⢧⡀⠀⠳⣄⡀⠀⠀⠀⢀⣴⠏⠀⣠⠞⠁⢸⠇⠀⠀⢰⠏
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⢿⡄⠀⠙⣦⡀⠻⢦⣀⠀⠉⠓⠒⠛⠉⢀⣠⠞⠁⠀⣰⠏⠀⠀⣠⠏
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠻⣆⠀⠈⠳⣤⡀⠈⠙⠓⠒⠒⠒⠚⠉⠀⢀⣴⠞⠁⠀⢀⣴⠏
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠻⣦⡀⠀⠙⠳⢤⣀⣀⣀⣀⣠⡴⠞⠋⠀⠀⣀⣴⠟
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠙⠳⢦⣤⣀⣀⣉⠉⠁⣀⣀⣀⣤⡶⠞⠋
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠉⠙⠛⠛⠉⠉⠉

I love TCs that take a game and completely re-work it. Those mods are always free of charge and are works of art rather than something for profit. They make completely new games out of old games with new textures, items, quests, stories, mechanics, locations and other gameplay elements. Multiplayer and Singleplayer alike. Here I list the ones I played and recommend. Most of them are not available on Steam itself but they work with Steam games. I will be adding more as I play through them. I have quite a few TCs I keep my tabs on but those that haven't been released yet are not included here because I haven't played them and thus cannot say if they are worth playing.
⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ The Wall of Fame

The Force Engine

Star Wars Dark Forces

Unity Engine

The Elder Scrolls: Daggerfall Unity

The Elder Scrolls: Morrowind

Arktwend

Myar Aranath

Tamriel Rebuilt

The Elder Scrolls: Oblivion

Morroblivion

Nehrim: At Fate's Edge

The Elder Scrolls: Skyrim

Enderal

Gothic II

Odyssee 2.0

Legend of Ahssûn

Chronicles of Myrtana: Archolos

Returning 2.0

Xeres' Return

Wanderer 1.5

Dirty Swamp 3.0

Velen 2.0

Diablo

The Hell II
lan capable

Belzebub (Tchernobog) HD mod
lan capable

Fallout 2

Nevada

Sonora

Resurrection 1.5

Olympus 2077

Fallout Tactics

The Sum

Fallout 3

Wanderer's Edition

Fallout New Vegas

Project Nevada

The Frontier

DOOM 3

The Dark Mod
a Thief inspired total conversion

Star Wars Jedi Knight: Jedi Academy

Escape from Yavin IV

Vengeance of the Sith

Movie Duels

Movie Battles II
online

Half-Life

Brutal Half-Life

Doom I&II
on GzDoom engine

Brutal Doom

Brutal Doom 64

Ashes 2063

Ashes Afterglow

Brutal Wolfenstein 3D

Wolfenstein Blade of Agony

Freedoom

Quake Champions: Doom Edition
online

S.T.A.L.K.E.R.

Anomaly 1.5.2.

True Stalker