Here's everything I'm aware of in terms of animatable properties, keyPaths, and key-value coding extensions. CALayer Animatable layer properties -- the other CALayer types below all inherit from CALayer, so these also apply to those:
anchorPoint
backgroundColor
backgroundFilters
borderColor
borderWidth
bounds
compositingFilter
contents
contentsRect
cornerRadius
doubleSided
filters
frame
hidden
mask
masksToBounds
opacity
position
shadowColor
shadowOffset
shadowOpacity
shadowPath
shadowRadius
sublayers
sublayerTransform
transform
zPosition
CAEmitterLayer animatable properties:
emitterPosition
emitterZPosition
emitterSize
CAGradientLayer animatable properties:
colors
locations
endPoint
startPoint
CAReplicatorLayer animatable properties:
instanceDelay
instanceTransform
instanceRedOffset
instanceGreenOffset
instanceBlueOffset
instanceAlphaOffset
CAShapeLayer animatable properties:
fillColor
lineDashPhase
lineWidth
miterLimit
strokeColor
strokeStart
strokeEnd
CATextLayer animatable properties:
fontSize
foregroundColor
CATiledLayer animatable properties:
I feel like tileSize is animatable, but documentation doesn't agree. CATransform3D Key-Value Coding Extensions:
rotation.x
rotation.y
rotation.z
rotation
scale.x
scale.y
scale.z
scale
translation.x
translation.y
translation.z
CGPoint keyPaths:
x
y
CGSize keyPaths:
width
height
CGRect keyPaths:
origin
origin.x
origin.y
size
size.width
size.height