B. Bill Blaster

B. Bill Blasters (presumably short for "Bombshell Bill Blasters") are yellow versions of Bill Blasters that shoot Bombshell Bills, appearing in pairs in Paper Mario and Paper Mario: The Thousand-Year Door.

Paper Mario
In Paper Mario, B. Bill Blasters are a yellow-tinted black color and appear only in Bowser's Castle. They act just like the Bill Blasters found earlier at the Koopa Bros. Fortress, but are much stronger. They have very high defense and health, and their only true weakness is piercing attacks, though they have a slight weakness to shrinking. Their only move is to spawn a single Bombshell Bill.

Paper Mario: The Thousand-Year Door
In Paper Mario: The Thousand-Year Door, B. Bill Blasters are now a very bright yellow and appear in the Palace of Shadow. They are now able to fire up to two Bombshell Bills at once, but are also now critically weak to many status effects, such as Tiny, Soft, Burn, and Freeze.