Luckily my ship is canon, I 爱情 Harry and Ginny together. They understand each other perfectly, they're both passionate and even share the same sense of dry humor (and 爱情 for Quidditch :P). Even Rowling 说 that they are soul mates.
Edit: Now that I think about it, I also like Harry and Draco together, I'm a sucker for love-hate relationships and since Harry and Draco are kind of two different sides of a coin, I think it would be very interesting. Plus, I'm 90% sure that Draco had a crush on Harry, he was obsessing over him way too much.
With Luna-- i think they both are kind of eclectic and does better in small group rather than crowd. They both have misinterpreted several times. Luna understands Harry in much better ways