Herein we first attempt to compare catalytic and electrocatalytic properties of the most commonly used peroxidase mimicking nanozymes based on transition metal ions, including magnetite, cerium oxide, and Prussian Blue. For the nanomaterials under consideration, the catalytic rate constant for reducing substrate increases upon decreasing its redox potential and reaches the ultimate values for Prussian Blue in the presence of ferrocyanide (k_cat = 3.8 s⁻¹ per single redox-active site). In addition to the highest k_cat, Prussian Blue nanoparticles in electrochemical sensors exhibit sensitivity to H₂O₂ by more than 3 orders of magnitude higher than other nanomaterials. Sensing properties of the electrodes modified with Prussian Blue nanoparticles appear to be dependent on their diameter; particles with diameter of 140 nm provide optimal sensitivity and lifespan of the corresponding sensor. The achieved exceptional (electro)catalytic properties of Prussian Blue nanoparticles open the prospects for their application as universal labels for personal analyzers with either optical or electrochemical readout.