Since taking Painting I in college, I have switched to using palette knife almost exclusively. I find that this change has made my work less fussy on minute details and more sculptural. I like the deliberate application of the palette knife to create edges, solid blocks of color, and texture. Whether you would like to tackle a still life, landscape, or abstract painting from a different angle, a palette knife could open new possibilities for not only what you paint but also how you paint it.
I have painted for several years, but I rarely use paintbrushes now out of personal preference for palette knife. The image above is a 3x4 ft. oil on canvas I painted called "Circus" using only palette knife.
Paint (acrylic or oil, something with a thicker consistency; avoid craft paint), palette knife (can be plastic or metal, any shape/size. I generally use the standard one), something to paint on (canvas, surface with applied shellac, etc.)