Even if a layer is filled with pixels, such as an image, a fill color, or both, the layer itself, allows other layers below it to show through when pixels on the top layer are erased or masked.

• Perspective Warp
• Transparency
• Skew
• Clone Stamp Tool

Lets you adjust the way objects in an image relates to the scene

• Transparency
• Dodge
• Perspective Warp
• Drop Shadow

Allows you to colorize by replacing the original color of an image with the foreground.

• Skew
• Clone Stamp
• Dodge
• Color Replacement

Used to make text or images standout

• Drop Shadow
• Motion blur
• Opacity
• Perspective Warp

Similar to a camera shake

• Drop Shadow
• Transparency
• Dodge Tool
• Motion Blur

Paints with a sample of an image

• Clone Stamp Tool
• Color Replacement
• Opacity
• Perspective Warp

Lightens areas in an image

• Transparencey
• Dodge Tool
• Drop Shadow
• Motion Blur

Used on one layer to reveal other layers beneath it  

• Opacity
• Color Replacement
• Liquify
• Skew

distorts the perspective of any graphic you're working with in general

• Skew
• Perspective Warp
• Transparency
• Drop Shadow

It will allow you to "push and pull" pixels any way you'd like.

• Dodge Tool
• Clone Stamp Tool
• Liquify
• Transparency