The HOA approves a particular design change for everyone except you. Or it refuses to grant you the same rights and privileges that have been extended to dozens of other owners. For example, you own an RV and want to park it in your backyard and the HOA, despite allowing others to park RVs in their backyard, refuses to afford you the same option and instead imposes countless fines, sends you numerous cease and desist letters, and threatens to seek an injunction against you in court if you don’t remove it from the community. Or the HOA refuses to grant you permission to install a pool in your backyard but all of your neighbors have installed pools in their backyard. Or the HOA adopts a rule specifically intended to target you or your property.
The examples are endless. While the HOA has the power to enforce validly-adopted rules and regulations, they cannot enforce those rules unreasonably or selectively. This can be is a powerful defense to any HOA enforcement action.