My picks from each season. I love those episodes equally, actually.
Season 1) Arghh (Texas was close, but I like nautical pirate motive from this episode, that sadly, not used much lately. GIMME ANOTHER TREASURE HUNTING EPISODES PLZ)
Season 2) Gary takes a bath (It's may sound as fairly strange choice, but I just adore this episodes. Comedy-wise, it's possibly my most favorite from ENTIRE series. It's just packed full of strong gags, without any filler or dull moment. This episode I really love to rewatch.)
Season 3) I had an accident. (It's so strange, but because of that I love it)
Season 4) Have you seen my snail? (Dunces and Dragons was close, but this episode wins by simple fact that I actually cry during song sequence. As pet owner it was really heart-wrenching and relatable.)
Season 5) Krabs Al a Mode (Predictable choice, but it was one of the few episodes that I watched all the time as a kid.)
Season 6) Not Normal (Good morale, good jokes and lack of gross-out, which for season 6 is astonishing. What else could you ask for?)
Season 7) The Abrasive Side (Mean-spirited humor done correctly. Really correctly.)
Season 8) Frozen Face-Off (Why not Hello, Bikini Bottom? I liked HBB too, but that's the thing, I hate Aaron Springer's art-style. Just hate it. And this is why I rank this episode lower personally. Those strange inexplicable feminine SpongeBob's mannerisms and cheeks just really annoy me. Also, why not It's SpongeBob Christmas? Because it's holiday episode, and that's means, I can't really watch it unless it's Christmas or Christmas eve.)
Season 9) Sharks vs. Pods. (This episode helped me regain interest in SpongeBob after my three years break. And I really love those music and dance-sequences.)
Season 10) Feral Friends (No need to explain this one)
Season 11) At least for now, It's Squid Noir. (I love jazz music, I love noir atmosphere and I really like mystery movies and novels. This episode - my dream episode. :patx: )