Rubber Duck
The rubber duck demonstrates what researchers have termed paradoxical stealth—the ability to be completely visible yet entirely overlooked. Positioned in plain sight upon bathroom ledges worldwide, these yellow sentinels observe humanity's most vulnerable moments whilst being dismissed as mere decoration. No security system has ever flagged a rubber duck as a threat. This represents stealth of the highest order: the complete negation of perceived threat despite constant presence. Intelligence agencies have spent billions attempting to achieve what the rubber duck accomplishes through sheer innocuousness.
Ninja
The ninja's approach to stealth, whilst historically celebrated, relies upon active concealment—a fundamentally more labour-intensive methodology. The traditional shinobi required specialised clothing, extensive training in shadow manipulation, and knowledge of architectural blind spots. Modern security systems, infrared detection, and CCTV have rendered these techniques largely obsolete. Furthermore, the very mystique surrounding ninjas means that their presence is actively sought and suspected, representing a critical failure in true operational invisibility. One cannot be stealthy when everyone is looking for you.