Here are my probably horrible ideas for some crests:  Flareon crest: immediately burns the holder upon entry and gives it a ground resistance 
	 
 
	Runegrigus crest: Cofagrigus but physical  Decidueye crest : contact moves now disable the last move used by the opponent  Purrseker crest : "claw" moves have +1 priority  Flapple crest: ignores hustle accuracy drop, but lowers attack by 10  Appletun crest: becomes neutral to ice moves, but gives it another weakness to poison moves  Samurott crest: slashing moves (razor shell included) lower the opponent defense by one stage  Zebstrika crest: adds fire type to its original typing and normal-type moves become fire-type   Mr Mime crest: upon switching in, mimic automatically becomes the last move used by the opponent  Quagsire crest: makes it also unaware of the field changes  Sandslash/Alolan Sandslash crest: activates sand rush/slush rush upon entry