[The Fifth Horseman]

If you append these to a Game Browser URL, you can add one extra filter where normally it would not be applicable. (eg, you can search for games associated with two genres)

There are more than these, but not all of them HAVE associated games.
Only one each of e, f, or x can be used at a time.

Alphabetized list:
1st-Person Perspective: x,7
3rd-Person Perspective: x,16
Action: x,1
Add-on: x,62
Adult: x,87
Adventure: x,2
Anime / Manga: x,57
Arcade: x,9
Baseball: x,32
Basketball: x,33
BattleMech: x,72
Bike/Bicycling: e,104
Bike/Bicycling: x,104
Board / Party Game: x,26
Bowling: x,88
Boxing: x,36
Cards: x,27
Casino: x,28
Chess: x,11
Coin-Op Conversion: x,10
Comics: x,68
Compilation / Shovelware: x,76
Cricket: x,73
Cyberpunk / Dark Sci-Fi: x,66
Detective / Mystery: x,55
Ecology / Nature: x,81
Editor / Construction Set: x,42
Educational: x,12
Emulator: x,90
Fighting: x,48
Fishing: x,18
Flight: x,19
Football (American): x,31
Foreign Language: x,85
Game Show: x,29
Geography: x,71
Golf: x,35
Graphics / Art: x,79
Health / Nutrition: x,92
Helicopter: x,56
Historical Battle: x,14
History: x,74
Hockey: x,34
Horror: x,83
Horse / Derby: x,91
Hunting: x,61
Interactive Fiction with Graphics: x,24
Interactive Fiction: x,23
Interactive Movie: x,60
Isometric: x,25
Licensed Title: x,82
Managerial: x,40
Martial Arts: x,39
Math / Logic: x,43
Medieval / Fantasy: x,78
Meditative / Zen: x,69
Mental training: x,107
Motorcycle: x,20
Music: x,59
Naval: x,41
Off-Road / Monster Truck: x,58
Olympiad: x,38
Paddle / Pong: x,64
Paintball: x,105
Persistent Universe: x,94
Pinball: x,53
Ping Pong/Table Tennis: e,103
Ping Pong/Table Tennis: x,103
Platform: x,21
Pool / Snooker: x,89
Post-Apocalyptic: x,65
Pre-school / Toddler: x,46
Puzzle-Solving: x,30
Racing / Driving: x,6
Reading / Writing: x,44
Real-Time: x,15
Religion: x,84
Rhythm / Music: x,97
Role-Playing (RPG): x,50
Rugby: x,75
Sailing / Boating: x,63
Sci-Fi / Futuristic: x,8
Science: x,86
Shooter: x,22
Side-Scrolling: x,17
Simulation: x,3
Skateboarding: x,52
Snowboarding / Skiing: x,95
Soccer / Football (European): x,49
Sociology: x,98
Sports: x,5
Spy / Espionage: x,93
Stealth: x,99
Strategy: x,4
Surfing: x,109
Survival Horror: f,102
Survival Horror: x,102
Tank: x,80
Tennis: x,37
Top-Down: x,13
Train: x,108
Tricks / Stunts: x,96
Turn Based: f,106
Turn Based: x,106
Typing: x,45
Video Backdrop: x,67
Visual Novel: x,111
Volleyball: x,77
Wakeboarding: x,110
Wrestling: x,51