Do you carry a credit card reader with you?

[Paul Sandhu]

These things are always in my pockets: cash, a pen, a knife, my phone and a credit card reader (Square).  There is always a receipt book in my vehicle.  That's how I roll.   

Cash is to buy things. A pen is to write out receipts. A knife is to cut open those hard plastic packaging on small items. The square is to collect rent.

What do you roll with, and why?