I have been using tab for fast target swapping for as long as I can remember and I know pretty well how to make it target exactly who I want by just turning the camera in the right direction.
However, I have a problem with pets, snakes, treants, etc. My mind ignores them, but hitting tab does not. Also more often than not they are directly in your face, making targeting anything at all besides them pretty difficult.

Is there any way to make tab targeting ignore pets, snakes, treants, etc? Basically make it ignore anything except players.

Open your options menu and click on keybindings.
Scroll down the list till you see Target Functions.
Change target nearest enemy player to whatever you want.

Alternatively you can add this in a macro as well just insert
/targetenemyplayer

This will ignore any pets, and totems only targeting players!