Adductor Pollicis
Hand
Tested with Froment's sign — if you compensate by flexing the thumb IP joint when pinching paper, ulnar nerve is damaged.
Function
Adducts thumb toward palm
Origin
Oblique head: capitate, 2nd/3rd metacarpal bases; Transverse head: shaft of 3rd metacarpal
Insertion
Base of proximal phalanx and extensor expansion of thumb (medial side)
Innervation
Deep branch of ulnar nerve (C8-T1)