Optimage - Advanced image optimization tool
Shrink Me - Compress images with one drag / click
ImageOptim - Faster web pages and apps.
TinyJPG - Compress JPEG images with perfect quality and file size
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
Aerate for macOS - Ridiculously good lossless image compression