The type of bag you carry can define your personality. It acts on your behalf as you walk into a room and therefore should exude character. The bag is also probably the only thing a man carries in all seasons.
With this in mind, the four bags every man should have are (click on image for details):
a tech bag for easy access to your arsenal of devices.
a unique brief case to be remembered by:
a tote for versatility:
and an elevated gym/weekender bag. The gym/weekender bag can be one in the same, as you want to be able to carry the gym bag to the office.
Bonus: Add a minimal iPad folio to the mix for protection and style.