Before September 2009 Synchro cat for sure was the top deck of the metagame, but it got a big hit with the September List. Cards like Summoner Monk, Rescue Cat and Cold wave were limited. And also Dark Strike Fighter got forbidden. It was a boss card for sure, lol.

The key cards of the deck pretty much were Rescue Cat, Summoner Monk, X-Saber Airbellum, Giant Trunade and Dark Strike Fighter to finish the things. 

You had several options for making some great plays, depending on the hand of course(you will see that in the video), but the most broken combo was with 3 cards. A Summoner Monk and 2 Spell cards:
Using Giant Trunade, Heavy Storm or Cold wave(Optional play, because pretty much the only cards that could stop you were Mirror Force, Torrential Tribute and Bottomless Trap Hole). Go for Summoner Monk and discard a spell for another Summoner Monk, discard another spell and summon a Rescue cat. Banish it for 2 X-Saber Airbellum's and synchro summon them with the Summoner Monk's for 2 Dark Strike Fighter's. Attack with them and then use their effects. Feel free to say "GG", because you just dealt 8000 DMG.

I won't go into deep analysis of the deck, just felt like posting this, because the video gave me some great nostalgic feelings.

About a comment on the video:
"Syncro Cat looks like such a random pile of cards, yet it just keeps winning. I love it XD"

Sigh, new players don't know what is like to build a real deck. You go on DN, type a single word and just add mostly every monster, lol. Also you add a Spell/Trap card and call it innovation. Amazing times for sure and if you played back then, I bet you had fun. Nowdays it's just full of those hmm, how do I call them? Idiots? Fine, idiots, like that guy:
https://www.youtube.com/watch?v=24wSdnk3DTI
"Combos August 2015" and he shows 1 combo. Such player, much fun, wow combos. Guess I had nothing better to do, being bored isn't good. Well, thanks for reading that and ignore my English, still sucking at it.

Feel free to discuss.

https://www.youtube.com/watch?v=QpRoGLU2xoM <---- Rescue cat ftk (1 card)

I am talking about the original Synchro cat, which is used in the video and not some versions. Plus, cards used in that video weren't released back then.

I'm aware XD, I just heard Synchro cat and thought about that ftk XD Thought it would be funny to share =) I remeber synchro cat back in the day, I also remember rescue cat in gladiator beasts.
Yeah I love seeing decks that do well that are unexpected hybrids or looks like random cards =)