Getting your app’s icon:
NSImage *image = [NSApp applicationIconImage];
Getting another app’s icon — this assumes you have a path to the bundle, which you provide as the iconForFile argument:
NSImage *image = [[NSWorkspace sharedWorkspace] iconForFile:@"path"];
According to this post, an app’s icon can be “overridden” by pasting an image into the “Get Info” window. In this case, the suggested solution is:
NSString *appPath = [[NSBundle mainBundle] bundlePath]; NSImage *image = [[NSWorkspace sharedWorkspace] iconForFile:appPath];