Well we haven't been together that long, so there's not a whole lot I have had the chance to do.
When we went out on our first date as an actual couple, I remembered he had mentionned before that he would LOVE to see me in heels one day, so I put together a cute little outfit and wore a pair of heels with it.
Another I've done was there was one day where he had a really rough day. he works the midnight shift, so is supposed to sleep during the day, but he couldn't get to sleep. He had already stayed up several hours later than normal to see me, so I offered to drive him to work and surprised him with a coffee. It wasn't a big gesture, but he thought it was really sweet.