For an Application concept I'm trying out (which I named 'Tarantula'), I needed to load menus dynamically, they would not be defined inside a NIB file. So I ended up with code like the following:

NSMenu      *menu;
NSMenuItem  *menuItem;    

[NSApp setMainMenu:[[NSMenu alloc] init]];

menu = [[NSMenu alloc] initWithTitle:@""];
[menu addItemWithTitle:@"About Tarantula" action:@selector(orderFrontStandardAboutPanel:) keyEquivalent:@""]; 

menuItem = [[NSMenuItem alloc] initWithTitle:@"Apple" action:nil keyEquivalent:@""];
[menuItem setSubmenu:menu];
[[NSApp mainMenu] addItem:menuItem];
[NSApp setAppleMenu:menu];

// Help menu
menu = [[NSMenu alloc] initWithTitle:@"Help"];
[menu addItem: [[[NSMenuItem alloc] initWithTitle:@"Tarantula Help" action:@selector(showHelp:) keyEquivalent:@"?"] autorelease]]; // Help
menuItem = [[[NSMenuItem alloc] initWithTitle:@"Window" action:nil keyEquivalent:@""] autorelease];
[menuItem setSubmenu:menu];
[[NSApp mainMenu] addItem:menuItem];

Sadly this doesn't work, for several reasons. NSApp's -setAppleMenu: is no longer defined, but can still be used by including the following code:

@interface NSApplication (NiblessAdditions)
-(void) setAppleMenu:(NSMenu *)aMenu;
@end

Then, whatever I tried (and again I'm using it outside the AppDelegate's awakeFromNib) I ended up with either a blank menu or an additional apple () menu appeared. Finally I concluded I should leave whatever was created by the NIB and I replaced:

[NSApp setMainMenu:[[NSMenu alloc] init]];

by:

[[NSApp mainMenu] removeAllItems];

after which everything started working.

So now for the end result. When the application starts, at first you'll see just the Application or Apple menu:

Then once the menu is replaced you'll see:

Which I think this isn't disturbing for the eye.