Team Fortress 2 (shortened to "TF2" by many) is a team-based multiplayer first-person shooter created by Valve. Starting its life as a far more gritty and realistic military shooter more in the vein of its predecessor (and having its life end at various points according to the community), it was initially released on the Orange Box in 2007. The game features nine different classes to play, all with their different features, weapons, and cosmetics.
The Handy Pardner is a PDA replacement for the Engineer that may have been considered for official addition to the game by Valve. The filenames of the textures for the associated Mini-Dispenser building were first discovered in the texture_preload_list.txt file which was added to the game in the October 28, 2015 Patch, and contained filenames for textures from Valve's own internal build.
Almost two years later to the day, the backpack icon, model and textures for the Handy Pardner were accidentally pushed into the game files in the October 20, 2017 Patch (Jungle Inferno Update). The image shown depicts the model for the cut mini-dispenser the Engineer could've had.