Spelunky is a Game Maker game about exploration, treasure, and dying to spikes. The game's source code was released on December 25, 2009, allowing many to make mods and look at the unused files.
The game had a remake, also called Spelunky. To avoid confusion, this older game is often called "Spelunky Classic" and the remake "Spelunky HD."
There are multiple isolated graphics within the source code, not tied to any object.
Not only is it not used anywhere, it's not tied to another object. There are sprites for a still hoop and it swinging.
There is a separate sprite for the rim, along with a "deflecting" sprite.
This odd "death mask" has a large sprite and a sprite that would go on the spelunker's head.
This ninja suit is unfortunately not used anywhere.
An...egg. It's oddly placed in the "Weapons" sprite subfolder, implying that it would be a thrown item like a rock that never found a use.
A yellow bell. This is placed in the "Treasures" subfolder, which means that it might have been a special jewel item of sorts.
Eight unused mushrooms, with their own subfolder to boot. It's unknown what these would be used for, although they evidently once had enough of a purpose to get their own subfolder.
An orange basketball.
The basketball can be thrown like a rock, and will not do damage to you. It will damage enemies, however. When you hold it in your hands, it bounces up and down as if you were dribbling it.
These athletic shoes are fully functional, but can never appear. The Jordans are basically upgraded Spring Shoes that make you jump over five blocks high. They cost $50,000 in shops, and even have their own pickup message, suggesting that they were removed late in development:
YOU GOT THE JORDANS! YOU FEEL LIGHT ON YOUR FEET.
A trap that will fall immediately when you are under it. It falls much faster than the ceiling trap triggered by the Temple idol. Unlike regular Crush Traps, you can walk on top of them without dying.
Unused Shopkeeper Text
There is some Shopkeeper dialogue that is never displayed without hacking.
NOW I'M REALLY STEAMED!
Displayed when you anger the shopkeeper via an invalid argument. The normal arguments are bombing, whipping, roping, stealing, and hurting a damsel.
I SHOULDN'T BE SELLING THIS!
Displayed when you view an item in the shop that isn't normally sold, such as the Sceptre.
JORDANS FOR $50000!
A buying message for the Jordans, obviously unused since the Jordans can never appear.