Bounces
These exercises are really difficult for both horse and rider, but it can improve both your and your horse's balance, plus, he will become more supple with bounces. A real-life example: I have ridden a horse known as the laziest possible and in one lesson I had to stop him constantly as he wanted to rush to the bounce.
Set it up
Set two small cross-poles (with maximum of 30 cm.) with no strides between, but remember to leave enough space for landing and jumping again.
How to ride it
Approach in a punchy canter with loads of impulsion. Once you have turned, raise in a two-point position. Keep the contact, but have your hands very soft and allow really much then jumping. Don't sit between the fences - instead, keep your two-point position until you turn again. Think about jumping one really big fence instead of two.
Too easy?
Build another fence no strides apart from the first two. This is known as "double bounce".