I think 'Quill' is a nice option. It's simple yet has a certain charm. Another possibility is 'Quest', suggesting a horse that's always on an adventure.
I think 'Quicksilver' would be a cool name. It implies speed and agility, which are important traits for a cowboy's horse. 'Quest' is also an interesting choice, as it makes you think of the horse going on adventures with the cowboy.
Some popular ones are 'Avatar: The Last Airbender' and 'Adventure Time'.
Some cartoon names starting with 'A' include 'Avatar: The Last Airbender' and 'Adventure Time'.
Well, there's 'Alvin and the Chipmunks', which is quite popular. Also, 'Arthur' is another one. These cartoons have different themes and storylines.
Well, one famous cartoon horse is Rainbow Dash from My Little Pony. Another is Spirit from Spirit: Stallion of the Cimarron.
Some examples are 'SpongeBob SquarePants', 'Scooby-Doo', and 'Steven Universe'.
Some examples could be 'X-Men' and 'Xiaolin Showdown'.
Some examples could be Sylvester or Speedy Gonzales. Sylvester is a well-known cat-and-mouse cartoon character, and Speedy Gonzales is a fast mouse.
There are quite a few like 'Peppa Pig', a popular kids' cartoon.
One that comes to mind is 'Justice League'. It has many superheroes and exciting storylines. Also, 'Johnny Test' is another cartoon name starting with 'J'.