There are also a lot of maps in the game. These are unlocked by beating maps from that map's difficulty category. On this page, I'll have my favorite map (or maps!) of each and every difficulty.
My personal favorite beginner maps are Tree Stump and Hedge. This is mostly because they are fun to play on and look pretty neat.
That's it. I just like 'em.
Now this is where I'll probably have more to say. My personal favorite intermediate maps are Spice Islands, Rake, And Streambed. I have seperate reasons for each of them; Spice Islands is mostly because I like most of the water towers in the game, Rake is because I REALLY like it's athstetics, and Streambed is cause it is probably my favorite map in the game.
On that note, maybe I'm just bad, but most of the intermediate maps are pretty fun.
This is where maps start to get pretty hard, but I still have some faves in this category. Speaking of, my favorite map in this difficulty category is Off The Coast. It's mostly because of the water in the map, but also cause I like how the map plays and looks, too.
Expert Maps. The hardest maps in the game, and the true tests of Bloons mastery. I have not beat much of these. I do have a favorite though, and it's Dark Castle. Mostly cause it's pretty easy.
For an expert map, that is.