If you're lithe enough to wear your shirt tucked in, you're open to a world full of fun accessories. Namely, belts.
Damn you, healthy, disciplined people, you get all the fantastic fashion accoutrements.
If you're one of those people, I suggest you pick up Anderson's Woven Belt ($100, Mr. Porter).
It's bright, it's colorful, and it says, "I'm skinny enough to wear one of these comfortably."