HT2738 - Your Minimal Kit

What is the least amount of gear you can get by with? This is an important question if you are traveling, have limited space, are concerned about weight, or want to simplify your choices in the field. What can you get by with? Two cameras plus three lenses? One camera plus one lens? Your iPhone? How do you make such decisions? Affordability? Complexity? The subject and locations? Looking back at past successes?