Edit: As of January 13/10, this record has already been broken. Youtube video evidence here: http://bit.ly/85QCQk
On September 6, a Smogon poster named peterko moved to the top of the board's unofficially official Battle Tower list when he had a streak end at 696 consecutive wins. Immediately after that, he began a new streak that would last over 3 months and came to an end last night... at 2,362 wins.
The team that was used:
Latias @ Choice Scarf
~ Thunder Wave
Registeel @ Leftovers:
~ Iron Head
Garchomp @ Lum Berry
~ Swords Dance
You'd think it quite crazy that 2000+ wins could come with 3 offensive moves, but it's possible.
The key is Latias, whose purpose is to allow for Registeel or Garchomp to set up. Tricking them into a move that Registeel can no-sell long enough to set up for 10 turns creates the ultimate tank, who can only be brought down by a critical hit, a Pokemon with 400+ Attack and a Choice Banded Earthquake (Rhyperior), a OHKO move or a Sunny Day-aided Fire move from something with Blaze active.
To last for 2300 wins, you have to have a lot of patience and quite frankly, enough luck to choke a horse. I can never get past 110 wins in the Battle Tower because even the best laid plans get thrown astray by a critical hit or a run of OHKO moves. Indeed, the streak finally came to an end at the hands of a Gliscor with Guillotine, U-Turn, Counter and Earthquake (holding a Focus Sash).
In 2362 wins, this Gliscor came up 10 times prior to the final match, and it never used Guillotine - it was always using Counter, where it would promptly get Tricked the Scarf and let Registeel set up for a sweep. The 11th time... Tricked into Guillotine, 1st hit breaks the Focus Sash, 2nd 3rd and 4th all hit. Quick as a flash, the streak is over.
The streak was so long it broke the Battle Tower - literally. After 1,743 wins (249 * 7), the Battle Tower loops back to itself. Although you don't get the Palmer messages the second time, when you get to 1764 you fight a Scientist with Palmer's exact Pokemon. The only thing I'm shocked about is that it didn't happen at 1785 (or 255 * 7).
I don't know if I'd ever be able to beat this streak even if I traded for max-IVd version of the Pokemon. Even if I had the same luck peterko originally had, I just don't know if I'd have the patience to keep the same streak going for 3 months.
peterko, we salute you.