The Weisenheimer is part of a sub-group of SMGs that only can spawn with a fixed-element Maliwan barrel. They feature the higher-than-usual elemental damage/second and element chance granted by the Maliwan barrel. These parameters achieve even higher values, if the SMG is equipped with a Maliwan grip.
Despite the low rarity designation of these weapons, their high elemental chance and status effect damage can make them excellent choices for combat until a more suitable (or less common, e.g. Legendary) weapon is obtained.
Other SMGs in this grouping manufactured by Hyperion include the Backburner (incendiary), Storm (shock), and Wellness (slag)/Cooler (cryo).
The Weisenheimer only comes in green or higher rarity.
The variants of this SMG in Borderlands: The Pre-Sequel commonly spawns with Hyperion's new-style materials and prefixes which are the same as in Borderlands 2.