Here's one from my new house. Pool equipment subpanel. Pool was built in 2004, been this way since it was built based on the initial breaker knockouts. Wild.
Worst to least bad:
1. Ground and neutral swapped
2. Pump / booster pump / heater all on single breaker and that breaker split across two single pole breakers
3. Pump not in GFCI (2011+ code requirement, panel is 04 so not as big of a deal)
4. Grounds double tapped across the bus bar.
Fixed it all and split the heater to a new circuit and added an extra breaker for future use.

