Since the shop is closing up, I went through and tallied up everyone's HFC submissions all the way through 399 to see who had the most. This list will only rank those who've sent at least 2 videos. The one hit wonders won't be here. That leaves the total at 58 people to submit multiple videos.
1. TreeHugger - 26 (Also has the most "WTF" or similar titles)
2. a3grimreaper - 14 (Side note that Jloco spelled my name different in almost every video)
3. MI2Lethal - 13
3. NeoRoman -13
3. LivingSky - 13
6. Jimbob1337 - 11
7. Ricco - 10
7. GurGnerd - 10
9. SugarSugar - 7
9. Benjamin - 7
9. assassinof1337 - 7
12. Jloco11 - 6 (Not accounting for HFC #400)
12. A7xDrumCovers - 6
12. Haymaker87 - 6
12. BrownPower - 6
12. ABiteSizeTaco - 6
17. EpicPineapple1 - 5
17. Haytred - 5
17. SmellyUndiesLUL - 5
20. TheBigB - 4
20. Goob876 - 4
20. Guywithnogamertag - 4
20. TheOnthunderbo - 4
20. Ford3984 - 4
20. xIvan14x - 4
20. VitFer2007 - 4
20. ModestDust - 4
28. Krusty - 3
28. Mahaffy - 3
28. TheWetOnion - 3
28. K00PTR00P - 3
28. Vegas Samurai - 3
28. MyGamingIsLegal - 3
28. BigMat - 3
28. hbkfc23 - 3
28. Sonwon - 3
28. Kinchyrk123 - 3
28. Rayne - 3
38. Mushashi - 2
38. GlennBacca - 2
38. TheDemented1 - 2
38. TheOjof360 - 2
38. Antbowman97 - 2
38. Reanimate - 2
38. TrewSaiko - 2
38. MSKW35T - 2
38. CPA2520 - 2
38. FroZzen - 2
38. Dragon the AI - 2
38. HelloDomo - 2
38. Bass2007Attack - 2
38. ZphykTESHD - 2
38. Nimma 1z Chaos - 2
38. 15charactersMax - 2
38. Pauly - 2
38. LocoChaz006 - 2
38. VisualFace - 2
38. PivotKid - 2
38. Swamps - 2
59. A Couple Hundred 1 Hit Wonders