For example, for fielders distracting the batter, I'm thinking of
- Physical distractions, like waving their arms, or everyone breaking out into the thriller dance, etc..
- Vocal distractions, like screaming "HEY BATTA SWING", or various explitives, etc..
Fielders can also distract runners by insulting their wives, or heckling in general.
I also wonder about the pitcher and catcher in particular. For example
- The pitcher pretending to have a spasm, before launching a "sucker punch" pitch
- the catcher clapping annoyingly, or heckling the batter in general
The only rule I'm aware of is balking, stopping the pitcher from feinting a pitch, but I'm pretty sure my suggested examples don't infringe on that.