When you ask most filmmakers what their next purchase is, you'll like hear an answer like "A new camera body, some lenses and better audio gear". It's always easy (and fun) to lust over new and expensive gear, but often we forget to buy the little things that make our life on set much less stressful. Although these tools are extremely affordable, they will often be the ones that make you a hero on set. Here are some tools that every filmmaker should have in their gear bag:
Swiss Army Knife - This seems like a no brainer, but I often hear someone yell "Does anyone have scissors" or "I need a "Phillips head screwdriver" while on set. Keeping this simple tool in your kit can save valuable time and make you a hero. Just remember to remove it from your kit when when traveling on a plane.
Magic Arm - A simple and effective way to attach gear to your camera at any angle. In my experience, this tool is invaluable when attaching a monitor or recording device to your camera.
Gaffer Tape - Despite it's name, gaffer tape can be used for so much more than lighting equipment: Taping down cords, setting marks for actors, labeling equipment and anything else you can imagine. Most importantly, gaffer tape has a big advantage over duct tape: It won't leave residue when removed.
Viewfinder - A major disadvantage of DSLRs and similar cameras is their lack of a viewfinder. Tasks like pulling focus or determining exposure are some of the cameraman's most important jobs, and something like a simple magnetic viewfinder will make a huge difference in your footage.
Extension Cords - A good extension cord will be with your for the rest of your career. It's a no brainer. Always carry one with you.
Sensor cleaning kit - In my experience, professional sensor cleaning is of the fastest ways to lose $50-$100. If you're changing lenses, it's probably worth investing in a proper sensor cleaning kit.
Gels - Whether you're trying to match color temperatures or create a bold and diverse color palette, a good set of gels is any gaffer's best friend.
Light Dimmer - Many lights, such as fresnels, are designed to keep a consistent wattage. Picking up a simple dimmer from Home Depot is a great way to add versatility to any light.
Bounce boards - A simple and cheap alternative to professional reflectors. Although any white surface will reflect light, it's best to find a large rigid piece of foam core that will stand up to the inevitable abuse on set.
Contract Signing App - This may seem like a strange addition, but apps like SignNow are incredibly low cost and valuable to any filmmaker. Creating templates such as Talent Waivers will ensure that you're always ready to film an actor or stranger.