One doesn't normally associate a chisel with painting, but this one has become indispensable in my work. I use the chisel to create lines in my paintings, scratching and scraping into wet paint, revealing the black base beneath in a process called sgraffito.
This process allows me to incorporate line into my paintings without the reliance of a brush. It mimics the application of stick medium held directly in the hand like charcoal or conte, letting me make a much more forceful and violent line.
My father gave me this chisel among some smaller ones that he used in the past for various metal and wood work. Below is a photo of it being used in a painting and a short video here.
Finally, an example of one of my paintings completed through this method.
Face, latex paint on canvas, 17" x 20", 2013