The #1 choice is a pair of gymnastic rings. Rings are inexpensive online and can be attached to anything stable. Trees and garage overhead supports, for example, can hold gymnastic rings. You can do almost anything with rings that you’d do with a bar. This includes pull-ups, chin-ups, and dips. Gymnastic rings are also an amazing investment if you’re traveling or want to work out at home. Rings do introduce a certain challenge, however. They rotate and require you to stabilize them actively during exercise. This is very useful in the long-term but should come with time and practice. Gymnastic rings simply offer some of the best upper body and core workouts around.