Details of the rankings below:  

• S3E01 - Ghosts
  • Good start with some drama (Shawn's dad and mom meet, following up the cliffhanger from the previous season).
  • Boneless!
  • Since Shawn is causing the problems, good to see that he had a backup plan with a higher up, should it fail. A tier

• S3E02 - Murder? … Anyone? … Anyone? … Bueller?
  • Solid episode. Almost good enough for S tier.
  • Lassie has a lot of fun arresting his date, after she is terrible to him.
  • Great Shawn speech at the end about Gus, with parents looking on.
  • Total John Huges homage. A+ tier

• S3E03 - Daredevils!
  • First appearance of "C'mon son", but said by the guest star.
  • Not a bad episode (are there really any?), but not my favorite.
  • Also, the most ridiculous Shawn vision ever - seeing an almost invisible gas leak on a moving motorbike from at least 200-300 feet away?
  • B tier

• S3E04 - The Greatest Adventure in the History of Basic Cable
  • Another great episode.
  • Steven Webber! I like him in almost everything he's in.
  • Change of pace, starting at almost the end in the interrogation room and working backwards.
  • Lots of funnies.
  • Almost S tier, but not quite: A+ tier

• S3E05 - Disco Didn't Die. It Was Murdered!
  • Good episode.
  • Loved Wally (Malcolm Barrett)'s way of speaking in this show.
  • Hilarious Blueberry ride pimping, and a funny commentary on racial profiling.
  • Fun episode. A tier

• S3E06 - There Might Be Blood
  • Not the strongest episode plot-wise.
  • Jane Lynch and Kristin Nelson make this episode with their spectacular performances.
  • Slightly odd romance developing between Lassie and Commander Dunlap was funny.
  • A tier

• S3E07 - Talk Derby to Me
  • Good Juliet feature.
  • Not really the strongest plot.
  • I can't be objective about this one (or, well, any of them really), but especially this one, as it was the first episode of Psych I ever saw and I didn't really get the show then. So it has soured me on it.
  • B tier

• S3E08 - Gus Walks into a Bank
  • Great episode!
  • A little hypocritical of Shawn to get so jealous of Juliet's date, but Shawn himself is dating others.
  • At the same time, it does reveal how deeply Shawn cares for Juliet, and I get that part of Shawn's issue is that it's specifically Luntz.
  • Good drama, good jokes, good jokes while experiencing the drama.
  • S tier

• S3E09 - Christmas Joy
  • Good one! The nighttime running in and out of doors bit was a great homage.
  • The Burton family lies being exposed was a good subplot. In fact, it seemed like the main plot!
  • Shawn trying to appologize “Gus… I’m…”, Gus says "good enough for me".
  • As far as your sleeping arrangements go, well, you don't have to go home, but you got to get the hell up out of here"
  • And then there's more! This was possibly the greatest Christmas episode ever.
  • A+ tier possibly S tier

• S3E10 - Six Feet Under the Sea
  • "Thesealion, what is that, French?"
  • Solid episode, A tier

• S3E11 - Lassie Did a Bad, Bad Thing
  • Great episode! Tempted to move to S-tier.
  • Nice to see them all rally around Lassie, despite his cantankerousness in general life.
  • A+ tier

• S3E12 - Earth, Wind and... Wait for It
  • Not a bad episode, not a great episode. Mostly meh.
  • Great guest stars!
  • Shawn just up and breaking into a wall with no real cause stretched plausibility quite a bit in this already implausible (but great!) show.
  • Tempted to bring it up to A tier just for Arsassin, Arsenurderer, Firearseman, Senior Pantalones de Fuego.
  • Maggie and Tim almost got hit by a doorknob flying from the exploding building in the final stunt sequence.
  • B tier

• S3E13 - Any Given Friday Night at 10pm, 9pm Central
  • Good amount of funny antics, but not much else to this plot.
  • James aparantly really does kick the ball and makes the kick.
  • B tier

• S3E14 - Truer Lies
  • Slightly incomprehensible episode. Not bad, just not one I'd pick for a rewatch party.
  • My favorite Santa Barbara street mispronunciations!
    • Anapamu - they say "Ahh nahh paah moo"
      • Actually pronoucned "Annapa-moo"
    • Carillo - they say "Ca-ri-ll-o"
      • Actually pronounced "Cah-reeo"
    • We don't have a Gardner street, but we do have a Garden street.
  • B tier (It would have been C level, but retroactively moved to B because of S5E14)

• S3E15 - Tuesday the 17th
  • Loved the fakeout horror followed by the real horror.
  • Much darker lighting, quite dramatic final showdown.
  • A+ tier

• S3E16 - An Evening with Mr. Yang
  • Spectacular episode. Serious Shawn. Excellent acting all around
  • Some funnies, especially Mary Lightly, and Gus’ attempts at levity in deadly serious situations.
  • Just amazing writing and adventure and everything.
  • Such a moment when Shawn decides to not play by Yang’s game and tosses the phone into the water.
  • Absolute S-tier.

....annnnndd a third one done!

A note on my tier list levels - S tier is reserved for something special, something extraordinary. The default Psych episode tier is A. A better than average Psych episode is A+. Something that doesn't quite live up to the high standards of most Psych's is set to B or C tier. C tier will only show up if needed. And none of these tier lists have D or F grades, because I just couldn't do that to a Psych episode.