The teaser poster calls to mind the poster for Fear and Loathing in Las Vegas. And the driver of one of the cars Rango hits towards the beginning is none other than the Good Doctor himself. Complete with sidekick.
"You see that? I knew it!"
Rango's situation is a nod to the Brothers Grimm tale of the Brave Little Tailor, including the "killing seven with one blow" detail.
An obscure (and somewhat random) one: in the sheriff's building when Beans, Rango and Wounded Bird are talking, one the wanted posters on the wall offers a reward (in water, of course) for the capture of Disco Lovejoy.
One member of Bad Bill's gang is a hunchbacked rabbit with a German accent named Kinski.
The scene with the hawk's feet protruding from the gravel, followed by the doctor declaring it dead, is reminiscent of the death of the Wicked Witch of the East in The Wizard of Oz.
Anyone else think of Raising Arizona when Rango was running from the hawk? Even the music got into the act. Not to mention when the... moles? rats? Whatever they are (Word of God calls them the "Inbred Rodents") first emerge to look for the bank.
Word of God states that Rango in general is meant to be a reference to Don Knotts in The Shakiest Gun in the West, while the "only one bullet" references Knotts' most famous character, Deputy Sheriff Barney Fife; the mayor's characterisation and Evil Plan heavily reference John Huston in Chinatown (he even says "the future, Mr. Rango! The future!"); Rattlesnake Jake is an allusion to Lee Van Cleef in The Good, the Bad and the Ugly; and the hawk that attacks Rango towards the beginning is a reference to Lee Marvin in Cat Ballou, featuring the same metal piece on his nose. Whew.
Was anyone else thinking of A Bug's Life when the mole family briefly trick Rattlesnake Jake into thinking there's a hawk?
When Priscilla points out the previous sheriff's tombstone, there's a grave in the background that reads "He's Dead, Jim". Also Waffles says "I am sensing hostility!" (while being attacked by the moles) which is likely a spoof on Councillor Troi.
Rango = Django (title character of the 1966 Spaghetti Western). Is also similar to Ringo, another Spaghetti Western character from 1966 played by actor Giuliano Gemma.
The Inbred Rodents themselves are very likely a much more family-friendly version of the cannibals of The Hills Have Eyes.
The marks drawn in the sky with a flaming stick that tell about Rango's "quest" include a TIE fighter.
When Rango goes to the Bank of Dirt after the townspeople learn that the bank has nearly no water left, it resembles the famous scene from It's a Wonderful Life.
The song which plays during Rango's highway crossing isn't on the soundtrack. It's "Finale" from the 2007 war drama The Kingdom.
Since the director knows about aye-ayes I'm going to count this as a Genius Bonus: in one scene Rango (prior to actually becoming Rango) imitates a gun-slinging, bowlegged beetle. In real life there's a large beetle that lives in the desert that's so poisonous and aggressive that one species of lizard imitates it as a juvenile — the only known case of a vertebrate imitating an invertebrate — by copying its markings and tall, bowlegged stance (at 1:30).
During the scene where Rango and the armadillo follow the walking cacti across the desert to find out where the water went, one of them collapses, referencing the "Rite of Spring" segment from Fantasia.