What is one of the most sensitive physical exam findings for testicular torsion?

Loss of cremasteric reflex. Several small studies have demonstrated close to 99% sensitivity.

The reflex is normally elicited by stroking or pinching the medial thigh, causing contraction of the cremaster muscle which elevates the testis.


Source

Ringdahl, E. and Teague, L. "Testicular Torsion" American Academy of Family Physicians. 15 November 2006.