1. The Thing He Can Fix
Maybe you have a partner who can change a flat tire on the side of the highway in the rain at midnight without even swearing once. If so, please share his contact information and available hours below in the comments (kidding!—mostly). But even if your guy is more of the "I made it better it by calling the mechanic" type, everyone has that one thing he can fix: a DVR on the fritz, a lackluster stew, a brokenhearted peewee T-ball teams' blues. If you find out, then you can more efficiently take advantage of your favorite person's skill set, true, but you can also present him with that great gift: a fixable thing.
2. Mustard or Mayo?
I just had lunch with a couple in the honeymoon-like throes of new romance and, half-jokingly, posed the question: "Do you guys know each other's mustard or mayo preferences?" My friend squinted at her love. "Well, I like anything," she said. "I don't care. Mustard's okay." He snorted. "Real English mustard, or that luminescent stuff you Americans call mustard?" (P.S. He's British.) She laughed, and I'm sure I didn't cause a rift in their budding relationship...but the point is that you should know your significant other's sandwich situation—as early on as possible.
3. His Obsession with Nikola Tesla, or Mantis Shrimp, or Whatever It Is
A strange side effect of long-term love is how the lovers in question can unconsciously calcify one another. "You are not into marsupials? Since when?" Or else: "I didn't know you always wanted to visit Galápagos!" We're usually aware of each other's career paths and hobbies, but what about the remainders? The oddball topics that make his ears prick up when he hears about them—for reasons completely escaping him. A visit to the nonfiction section of a library or bookstore can do wonders. Bonus: What you learn can kindle conversation on those date-night dinners when you stare off into space trying not to complain about work or talk about the kids.
4. His Blood Type
You know his heart, but you may not know his blood type. When it comes to relationships, the particular is grand, but the mundane is romantic.
Next: What's his ranking on the good Samaritan index?