Erza

Erza had thought long and hard about her guild mark before asking for it to be placed at the top of her left arm. Macao, who was doing it, looked puzzled.

"But Erza, everyone knows you're right-handed..." he began.

Erza just smiled. After all, she didn't just have swords and armour in her private universe. There were shields as well.

So the mark went on her left arm, her shield arm, and she swore to die defending the guild that had always shielded her in return.