One herb that smells great and grows REALLY well is mint. I had a plant in my window box and it got OUT OF CONTROL (but that was good because more for the buns!). Also, I found that basil grows really well too, and both of these also smell great.
My bunnies really like the botanical hay, but I am still debating about whether or not it is worth the price. I buy Timothy hay currently, in bales, so my hay is only about $10/bale, and I don’t know if the Oxbow botanical hay is worth it, if you are in an area where you can grow nice herbs and veg. If you’re located in the city and somewhat “concrete locked” then its probably IS worth it, but as an alternative you can still grown flowers, herbs, and vegetables in garden boxes like I did in LA, and the bunnies REALLY enjoy the fresh veg even more that the dried flowers in my opinion (which is based off of Kramer’s opinion, which is, if its not straight from the garden box he doesn’t eat it!)