Mazda : Current logo is quite recent, and is a kind of M-shaped wings. They had another one in the 90s which was too close to Renault logo.

Mitsubishi : The name means "three diamonds", hence the logo...

Saab : Swedish Kingdom emblem

Opel : Originally a zeppelin, which became more stylized, not sure of why it become a lightning.

Subaru : Japanese name of a star cluster (Pleiades)