Tethermine

"Catch players off guard with your tethermine!" In-game description

The Tethermine is the default slot 3 weapon for Demoman which acts as a trap that attaches itself onto enemy players that get too close to it, which then explodes after a few seconds, dealing extreme damage.

It resembles a black ball with multiple gray circles on its surface. It has a team colored band in the middle and some sort of rectangular object on it, presumably has something to do to arm it.

Tactics

 * Its arming time is short enough to be able to arm itself upon impact, when thrown high enough. Use this fact to actively use the tethermine against moving enemies.


 * Throw it on areas where the enemy cannot see it, such as behind corners or objective points.


 * The Tethermine can be destroyed, which is its biggest weakness. It can also be wedged between an object so that it doesn't damage the player that it is attached to. But it can still be a viable weapon against enemies, provided they don't know how to counter the Tethermine.
 * Classes such as Shielder and Sniper would often struggle trying to counter it, as they have low mobility and lack of explosive/melee weapons, although Shielder has the frag grenade and morning star, which can destroy the Tethermine.

Trivia
Contrary to popular belief, it isn't a soccer ball.