Best toy I find for a rabbit is another rabbit - honestly! So long as a rabbit experienced vet can neuter/spay both of them they entertain each other better than any toy can.

I adopted these 5 girls for my boy this week as he lost his brother last week and was very depressed - just sitting around not doing much...The girls were too much for him though - he got stressed and sat around sulking or trying to bite them through the wire mesh - so now I've made the boy a house rabbit and the girls have his shed...

But he doesn't have the run of the house - just a cage in the kitchen and run of the patio shared times different to the girls - He loves running around smelling where they have been and what they have been digging into, urinating, scent marking etc - He's had more exercise today, following the scent of these girls, than since his brother died nearly 2 weeks ago...Bunnies are social creatures

PS - the other problem with a wheel for exercise would be the horrible injuries a bunny would suffer from when it got its back feet caught between the rungs of the run - Solid type wheels are recommended for small animals for the same reason - and you couldn't make a solid wheel with a diameter of 3 feet - and if you did somehow it would simply be too heavy for a rabbit to turn without strain - most rabbits would just decide to chew it up for fun