Rectifiers and switching diodes for protection and ORing.
Rectifier diodes block reverse voltage on supplies. Switching diodes recover faster for PWM and snubbers. Schottky parts lower Vf at the cost of leakage.
Match If, Vr, and trr to the circuit. For USB protection, use parts specified for the standard you implement.
Widely used examples
Examples for orientation only. Not an offer, stock list, or complete parametric search.