Since reading the weekend themes proposed by 
What do you think is brilliant in design, form or function? List the physical elements and explain why?.
For my entry I had thought of several accessories and tools that I consider brilliant for their function and form in terms of grip and ease of use, initially my selection was the zigzag scissors, retractable tape measure and a sewing guide, after analyzing other accessories in my sewing box Eureka! I found two of the tools that I use the most in my sewing work, they are the thread cutter and the seam ripper, both are very useful when you need to unravel a seam and are also helpful for small openings in the fabric, they are tools that must be handled with care because they are sharp and can cut and puncture, From experience I can say that the punctures are painful, but if you are careful in its use there will be no accident, when I started sewing projects I got punctured several times because I did not know how sharp is the edge trimmer, over time I have learned to use it and very carefully I am unpicking, so far I have managed to do it without punctures and I hope to continue like this.
On several occasions I have told my classmates that apart from the sewing machine and scissors, these are my favorite tools for sewing projects, without them it would be impossible to mess up bad seams and achieve a better finish, I think the person who devised these tools deserves great recognition for the versatility and usefulness they have in sewing projects.
The seam ripper is one of my greatest allies for sewing projects, when I start a work is always on my table, its physical elements are:
It comes in various sizes according to the required function and type of fabric, the smallest is for light and thin fabrics and the other for fabrics such as jeans and canvas, in the first case it does not require a great effort to remove the seam but if precision to not prick with the small blade, the largest demands strength and precision by the texture and thickness of the fabrics, these regularly have many threads, which can come while unpicking and in some cases the fabric breaks.
The size is adequate and easy to handle, although if I could add something, it would be a softer and more flexible rubber handle.
The design of the U-shaped blade is perfect for moving along the seam and breaking the threads.
The protective cover is very important because it avoids pinching when we look for the accessories in the box.
In addition to breaking up the seam, it can be used to open buttonholes, small openings when a piece needs to be turned over, among other things.
The thread cutter is another of my favorite tools. Here's why:
It's a type of small pair of scissors with very sharp blades, which allow you to cut threads comfortably.
It's retractable, and when you press it to cut the thread, the strip in the center joins the side bars, making it easier to cut the thread. This can also be done with scissors, but with this tool, it's easier, as the scissors are very large and this tool is the perfect size for cutting excess thread when starting and finishing a seam.
Like the thread cutter, it can also be used to open buttonholes and small openings.
An important point is not to cut them with this tool. I did it several times and it got damaged. I don't think it's designed to cut thick pieces, only threads.
I really like its design and in terms of utility I wouldn't add anything, being retractable it allows for simple and adequate handling, you just have to be careful with the blades because they are sharp, a small oversight can cause an unwanted cut in the fabric, also carelessness when handling the different tools is never too much, with practice and time using these tools I think we learn to handle them without problems.
Blessings!
Translated with https://www.deepl.com/translator
All images are my own