I really like Calvin Klein for his classic simplicity. I also think Prabal Gurung designs some great pieces that work well for me. My mom has such great style she's my biggest influence.
I'm a fan of designers and clothes that look beautiful but more importantly make me feel beautiful and confident. It's why I've always loved Stella McCartney and more recently Prabal Gurung. Their pieces are cool yet timeless and the fits are effortlessly flattering.