Bottle openers, pliers, bare hands (force your fingers into the velvet trap and bend the cassette open), teeth and the dedicated Ilford cassette tools all work fine for cassettes. But I'm with the 'retrievers never work' school. Much better use the method below for leaving the leader out, if you don't have an auto function to do it.
When you're loading film on a manual rewind 35mm camera, once you've closed the camera back and wound on a couple of frames (in order to reach unexposed film and make sure the roll has been taken up), use the rewind lever to gently rewind the film until it becomes tense. Doing this means that when you wind on to a new frame the rewind lever will rotate confirming that the the take up mechanism is operating correctly (hands up all those who, on some occasion, have found that they've been shooting away blithely whilst no film was being pulled through the camera). More importantly, because of the tension you've put into the system, when you reach the end of the film and rewind you should be able to feel the exact moment when the film leader has been released from the winding mechanism. At this point stop rewinding and remove the film from the camera - the leader should still be hanging out of the cassette.
Remember to crease or fold the leader before you return it to your camera bag - you don't want to load it again by accident. Old pro's often left the leader out like this and would use the trailing end to make notes (such as 'exposed at 1600iso' or 'underdevelop -1'), others would use the number of folds they made on the leader to indicate development (two crimps = underexposed 2 stops etc). The beauty of this is that you can use any old pencil or biro, no need to rely on special felt tips in order to write on glossy cassettes.
Adding tension also enables you to unload a film mid roll, should you wish to change films and then reload it accurately at a later date. Just make a note on the leader of how many frames ("x" frames) you've exposed and then, when you reload it, close the aperture to it's smallest opening, set the highest shutter speed and, with your palm tightly covering the lens fire off "x +2" frames, then carry on shooting. (You can use a lens cap, instead of your hand, but I hate them : They get lost, they're hideously expensive and, if you're shooting from the hip they can mean the difference between being Henri Cartier-Bresson or just another a bloke with a camera round his neck...
Regards
Jerry