Eyes, nose, ears, mouth.
X-ray/night/infrared vision. Reactive filters that protect against extremes of light (sudden brightness, direct lasers, flashbangs...), scent (offensive/sickening smells), sound (peaks above 120 dB SPL), and taste (again, offensive/sickening tastes - useful for getting those vegetables down!). Optional multiband audio compressors that can selectively amplify certain frequencies while attenuating others - allowing one to (for instance) hear a particular person's speech more clearly, or to simply make music sound better (for instance at live gigs with poor sound). Scent enhancers allowing one to detect scents as well as dogs do.
The benefits really are endless.
EDIT: And most of these benefits are attainable with modern technology.