Well its a tie between Reef Blower (since I will take it that Mr.BoxBox voted for Reef Blowers as well) and Krabs vs Plankton. I pick the underappreciated Reef Blowers.
Season 1
6. Mermaid Man and Barnacle Boy
Season 4
61. Shell of a Man
62. Krabs vs. Plankton
64. Good Neighbors
67. Enemy In-Law
68. Patrick SmartPants / SquidBob TentaclePants
70. Ghost Host
71. Chimps Ahoy
72. Karate Island / All That Glitters
73. New Leaf / Once Bitten
74. Bummer Vacation / Wigstruck
75. That's No Lady
76. The Thing
77. Driven to Tears / Rule of Dumb
78. Born to Be Wild / Best Frenemies
79. The Pink Purloinier / Squid Wood
80. Best Day Ever / The Gift of Gum
Season 5
82. The Original Fry Cook
83. Rise and Shine / Waiting / Fungus Among Us
84. Boat Smarts / Good Ol' Whatsisname
86. Bucket Sweet Bucket
87. To Love a Patty / Breath of Fresh Squidward
88. Money Talks / Slimy Dancing
89. The Krusty Sponge
90. A Flea in Her Dome / The Donut of Shame / The Krusty Plate
93. Picture Day / Pat No Pay / Blackjack
94. Blackened Sponge / Mermaid Man vs. SpongeBob
96. Pest of the West
97. The Battle of Bikini Bottom
98. Whatever Happened To Spongebob? (WhoBob WhatPants)
99. SpongeHenge
100. Banned in Bikini Bottom / Stanley S. SquarePants
Season 6
102. Penny Foolish
103. Spongicus / Suction Cup Symphony
104. Gone
107. No Nose Knows
108. Plankton's Regular
109. Boating Buddies
110. Grooming Gary
112. Choir Boys
113. The Card
Season 7
114. Dear Vikings
115. Cephalopod Lodge
117. Professor Squidward
118. Pets or Pests/ Komputer Overload
119. Truth or Square (unaired)
121. Shell Shocked / Pineapple Fever
122. Gullible Pants
123. Squid's Visit
124. Someone's In The Kitchen With Sandy
125. To SquarePants or Not To SquarePants
126. Growth Spout
127. Greasy Buffoons (unaired) / Stuck In The Wringer