Speaking on behalf of my gender, the man in your life would love flowers or chocolates tomorrow. But since we have our gender roles to play (and this is a tech site), any one of my Products of the Year or one of these male-appropriate gadgets would make great "I love you" Valentine's Day gifts.
Clothes? For Valentine's Day? Not exactly romantic, I grant you? But this is coolest of all possible shirts. It may not look like it, but hidden inside this otherwise non-descript Scott eVest Explorer shirt ($85, available in Flax, pictured, or Mocha, a light brown) are 19 pockets – you can see them all on the x-ray view here (I bought one and am still counting pockets). And nearly all the pockets have a button loop to pass through headphone cords that stays hidden inside the shirt until it emerges from your collar. It'll be his conversation piece for months.