Personally, I like to juice up several different kinds of fruit and vegetables - which may include various combinations of bananas, red bell peppers, apples, carrots, celery, broccoli, spinach, parsley, tomatoes, cucumbers, etc.
Be sure to buy organic versions of the 'dirty dozen:' the fruits and vegetables that, when grown conventionally, are loaded with pesticides and chemicals: Grapes, apples, lettuce, bell peppers, carrots, nectarines, peaches, strawberries, pears, kale, and celery.
I'm obsessed with broccoli, carrots, celery, string beans, snap peas, black kale, brussels sprouts, cabbage - I could go on! They used to call me 'rabbit' when I was a kid. I hate mushrooms, though. I apologize to fungi lovers, but this way, there's more for you!