A new piezoelectric crystal, KCsMoP₂O₉ (KCMP), was successfully grown by the Kyropoulos method. The electro-elastic properties of KCMP crystal were characterized by the impedance method. The full set of elastic constants was determined by solving the Christoffel equation. Remarkably, the crystal exhibits a large face-shear piezoelectric coefficient of d₁₄ = 16.2 pC/N, surpassing that of the extensively studied ordered langasite crystal Ca₃TaGa₃Si₂O₁₄ (d₁₄ = 10.4 pC/N). A fundamental shear horizontal (SH₀) wave piezoelectric transducer was developed, leveraging the face-shear-mode of KCMP wafers. Finite element simulations have conclusively demonstrated the KCMP-based transducer's exceptional ability to efficiently excite and capture the pure SH₀ wave, independently along two orthogonal main directions (0°/180° and 90°/270°). These results were subsequently corroborated through experimental validation at temperatures up to 300 ℃, highlighting the considerable promise of KCMP crystals for utilization in non-destructive testing and structural health monitoring applications.