Well, fair enough - I suppose a deity who used a gladius would have a preferred weapon of "short sword", since that's the D&D weapon stat block it falls under.
But no priest of Tharizdun would be caught dead using a straight dagger
The Realms have Ghaunadaur, also called "the Elder Eye", and I think he was described as an Elemental deity in some novels. He's also That Wchich Lurks. He's the god of Slimes (and all that) with Cavern, Chaos, Drow, Evil, Hatred and Slime as domains. He uses an amorphous tentacle, though his clerics (or at least those who didn't turn into oozemasters) use a warhammer instead.