The Stielhandgranate is carried by only one enemy, the Panzergrenadier. They use these stick nades to clear trenches and blow up cam nets. Damage is increased within trenches and mortar pits. Watch out for the Panzergrenadiers who use these, they will wipe out your soft defenses that are around the 200 pixel line. Stielhandgranates are very deadly against your infantry and can do minor damage to your vehicles. If you are lucky your frenchie can blow up an ammo dump and stop Panzergrenadier's from being equipped with them.
Be wary of Panzergrenadiers in higher waves, as they can throw many grenades within a short span of time. What's even worse, since these travel in vertical lines, they can blow up anything and anyone along that line.
Who uses this?
The Stielhandgranate, or Model 24 grenade, was invented in 1915 and has such names as the "potato masher" and "stick grenade". It used the common German friction igniter and was an offensively oriented grenade, relying on blast damage rather than fragmentation. However, in 1942, a serrated fragmentation mechanism was installed in the grenades. Instead for pulling a "pin", like traditional hand grenades, the operator twisted the metal mechanism at the bottom and pulled a cord that came out of the handle instead.