On the right, forsythia twigs cut on an angle. They are usually hollow inside so will hold some ink or paint and make good pens.
On the left and below second on the left is a brush I made using some dried ornamental grass stalks cut from the garden. They are taped to a forsythia twig with masking tape and make some nice grassy effects in a painting.
Above I have had some teasels growing in the garden. They got up to about 4 ft. I left them over winter for the birds to take the seeds. When I cut them down I saw that the stems were hollow and larger than the forsythia stems and might make some interesting marks.
Above from the top going clockwise, pieces of old credit type cards whole or cut down make great tools for spreading acrylic paint.
A fork or comb are good for scratching back into wet acrylic paint.
The corks can be used for printing either as they are or with nails or string added. I made these for use with batik wax or they can be used with acrylics.
My acrylic painting below was mainly done with the credit card and the fork.