Contrary to your his dad's advice, a well groomed man needs more than three things in your medicine cabinet. These are the basics.
Shampoo and Conditioner - Yes, you want both. Conditioner brings out the shine and softness in your hair, which shampoo can strip away.
Deodorant - This is sort of a no-brainer. Experiment with deodorants and antiperspirant brands until you can find one that works all day, and smells great after 5pm. You can often find a deodorant that matches your favorite cologne.
Gentle Soap - You're not removing lice in the army, you're having a shower, hopefully within 36 hours of your last one. Ditch the harsh soaps for a gentle, thorough clean. If you plan to use the same soap for your face and body, ditch the heavy body washes and go for something mild and unscented.
Moisturizer with Sunscreen - On your face. Every day. Period. The basics of sunscreen and aging are known. You can even get manly products in manly tubes, so there isn't any excuse for neglecting your face.
Lip Balm - Unless you are superhuman, you will occasionally need this.
High Quality Razor - Cheap plastic razors will have their revenge on you. You'll need to shave the same spot more than once, increasing the irritation to your face. If you can afford it, the expensive razors and blades are actually better, and your face does stay smooth longer.
Shaving Balm - If you find you get irritated after shaving, try a gentle shaving balm, instead of aftershave - throwing scented alcohol on an irritated face isn't always your best option.
Wide Tooth Comb - Try coming your hair in the shower, with conditioner in. You will break fewer hairs. Brushes and small combs are not necessary unless you are caring for long hair.
Styling Product - Hair gel, pomade, wax or spray - it's up to you. Most men use some product to keep their hair in place during the day. Keep it simple and find one product that covers your needs.
Manicure Set - Take care of your hands. File off any broken or rough edges. Clean the dirt from under your nails. Clean, well kept hands are noticed.
Tweezers and Trimmers - Take a good look in the mirror. Is there hair in places that might not be the most attractive? Coming off of your ear? From your nose? Between your eyebrows? Stray whiskers on your face?
Get the right equipment and fight off your personal jungle - no one wants to be with the Wolfman, or their crazy grandpa. Tweezers, trimmers, small scissors - get them and use them.
Cologne - You knew that.