[Crest Suggestions! (CLOSED)]

Ok, got a few more.
Goodra Crest: Gains water type. Sets up rain upon being sent out. Boosts special moves in rain by 33%

Floatzel Crest: Attack is boosted by 15%. When in rain, all special moves become physical.

Samurott Crest: Uses swords dance upon being sent out, if its in its moveset. Sword/slash/cut moves do 20% more damage. If it lands a super-effective move, the opponent gets one random stat lowered. If it lands a not-very-effective move, its gets one of its stats lowered. If it gets a crit, regardless of effectiveness, the oppnent's defence gets lowered.

Stoutland Crest: Uses Odor Sleuth upon being sent out, even if it doesn't have it in its moveset. Does 20% more damage to an opponent affected by Odor Sleuth, regardless of type, and receives 10% less damage from them as well.

Reuniclus Crest: Trick Room is activated upon being sent out, and lowers its own speed and boosts his opponent's by two stages each. As long as Reuniclus goes first, all moves it has are special, and all psychic moves, even the opponent's, do 15% more damage.

 

Goomy Crest: Becomes Goomink. Gets Fighting type. Has moveset replaces by Sacred Sword, Swords Dance, King's Shield, and Leaf Blade. Gains Justified.
 

[Crest Suggestions! (CLOSED)]

A few ideas for my favorites
Jolteon Crest: Special moves are boosted by 10%. Makes all physical moves with a power of 80 or lower special.

Luxray Crest: Gives Dark type. Switches Sp. Atk and Speed. All biting moves have 1+ priority.
 

Roserade Crest: Boosts damage from absorbing moves and changes the amount healed to 67%. Also heals status effects if it heals more than 33% of its health.