Answer: Demodex mite
These ubiquitous ectoparasites are found on most individuals in hair follicles (Demodex folliculorum) and sebaceous glands (D. brevis) and are considered to be normal skin flora. As such, they are commonly seen by dermatopathologists in skin biopsies.
I particularly like this photo because you can make out the appendages and mouthparts of this mite:
The intact organism can be seen on my previous CASE 58.