TF2 Merc Slapper is a mashup of Amarillo's Butt Slapper and Team Fortress 2. The arena and the slapping stay exactly as the host built them - what changes is who is standing there.
A TF2-style class select opens first: nine portraits, one for each merc. Pick one (or let it auto-pick) and you drop straight into the arena.
All nine mercs - Scout, Soldier, Pyro, Demoman, Heavy, Engineer, Medic, Sniper and Spy - stand in as the slappable victim, built from TF2's real model geometry with their real textures.
Real TF2 reactions: every slap makes the merc wobble and squash, yell a real pain voice line, and - when the crit gods smile - flare up with the crit glow and the crit sting. Land ten slaps in a row and you get the domination sting.
What you need
Amarillo's Butt Slapper (the host - this is where the mod installs)
Team Fortress 2 (the companion - every model, texture and sound is read at runtime from your own TF2 install; nothing from TF2 ships with this mod)
Controls
Click a portrait on the class screen to pick your merc (auto-picks in 60 seconds)
C - reopen the class screen and switch merc
1-9 - quick-switch class
Click / slap the merc like normal - everything else is the host game
Credits
Amarillo's Butt Slapper by AmarilloArts
All merc models, textures, portraits and voice lines belong to Valve (Team Fortress 2)
Mashup code (the VPK/VTF/MDL readers, the picker, the reactions) by Melty