As much as I think Shawn and Juliet are cute together and have great chemistry, I think that Juliet and Lassiter makes more sense. Canonically, Shawn/Juliet and Lassiter/Juliet are more or less tied, but in different ways. Shawn flirted with Juliet and asked her out at least a dozen times, and she actually asked him out at the end of the season 3 finale (3x16). But Shawn was already on a date, and her heart was broken. Guess whose heart was broken just an episode before when he received another request to sign divorce papers instead of a second chance (3x15)? That's right, Lassiter.

Juliet and Lassiter have the perfect amount of awkwardness going on. He's already met her family -- Shawn couldn't go because he was having dinner at Gus's house (2x10). She actually gave him a hug when his solo case-solving streak was ended by Shawn (well, she offered one, which he accepted) (2x02). She noticed when he was wearing a new tie (2x15). She's always broadening his horizons a little (her pointing out the scenery of the spot where he was sitting and eating at the beach (1x05)). She tried very hard to learn about him and throw him a surprise party for his birthday (1x14). She was jealous when he pointed out how attractive a museum curator (2x16) and a commander (3x06) were. She brings up, after only knowing him for 2 episodes, that she's not really into dating coworkers (he dated his last partner who, by the way, was blonde too) (1x04). In 2x03 Psy vs. Psy there is a guest character who is supposed to look a lot like Lassie that she kind of digs, even if he did come off a little creepy.

He was very upset when she had a temporary partner reassignment during his period of being suspect for a murder (3x11). He knows what her hair smells like (2x12). He called her "above all things, not hot" (2x12) and refused to say she looked pretty during the speed dating (1x11). He enjoyed when Shawn made fun of her older boyfriend Commander Luntz (3x08). She worries about his personal connection with the lodge case, really looking sympathetic when his father-in-law got onto him about the marriage, and helps Lassie ultimately try and impress him (2x14). Lassie is like totally in love with her "bad cop" side when he's teaching her (2x07). Also, the kids ask if they're together and then say she's totally out of Lassie's league. Lassie doesn't want to tell fellow officers why the suspect got away, because it would make Juliet look bad (2x09). In 2x15 Black and Tan: A Crime of Fashion, Juliet gets a hot new outfit to "dress to arrest". All three of the guys (Shawn, Gus, and Lassiter) stare at her, but the scene ends with the other two having already walked off as she walks away, and Lassiter still staring. There's also a hilarious line where he tells her she "can't do that", referring to the outfit. Have to love it.