Solving a boredom issue

when I ride my young gelding... with other horses, we sometimes drop back and do circles, serpentines, and figure eights while everyone else goes on.
 
I also mave him to flex his neck around quite often when we ride and have him keep to a walk when the other horses run off and leave him by doing serpentines and figure eights.
 
Don't know if that helps, but I'm not much for 'games' undersaddle and stuff... Lol.

When I have a horse that is really getting bored with everything I like to put them on calves.  Let them track that calf all over the arena and after the initial OH MY they really like it.  That way you can still work on stops, rollbacks, and things like that and now there is a reason for doing it. 
 
Another thing is find a real chalanging trail for them to follow.  I go down to Shawnee National Forest and its really hilly with lots of rocks and creeks.  Seems to clear their minds and helps them understand to watch their feet.

I knew a reining trainer that kept her stallion fresh for competition having him work at other riding activities.  She said he really liked to run barrels - he wasn't a real contender, but the idea was to give him different jobs to keep everything fresh for him.  She also did trail classes and trail riding - anything to interest them.

 Hey, my horse loves to play soccer she will chase the ball all over the place. The ball is huge! Now when I try to run barrels she think that they are ball and you need to run into them!

i play tag with my horse lol then he starts playing with me like im another horse, which is really scarey and dangerous i know but he has no one else to play with so, anyhow when i play tag with him i make sure to get his feet moving and keep his attention forward,
when i babysit i will put one of the kids on his back and we all play tag the kids have to get him to tag someone else which is good for them and good for him,
i also am working on some tricks that ive seen, like bowing between his legs, im still workin on how to get him to get down on his knee for a full bow, but its good work for him, i also do voice commands, i have him follow me and ill tell him whoa then back and turn him around and what not,
i was also thinking about teaching him how to do that dance thing....i cant remember the name now but its a song and it tells you what to do i think the steps are to the left, to the right, take it back, one hop, stomp with your right foot something like that i thought that would be fun lol
good luck!