gistfile1.m

#import <Foundation/Foundation.h>

@interface WTF : NSObject
-:x;
@end

@implementation WTF
-:x;
{
  return x;
}
@end

int
main()
{
  NSLog(@"%@", [[WTF new] :@(42)]);
  return 0;
}

gistfile2.txt

$ /Users/eloy/Code/ObjectiveC/objc-run/objc-run test.m 
2014-03-28 12:53:53.665 test[93801:507] 42

Now make a method that accepts no arguments ;)

It still has a name. Its name is :.