Yesterday, I noticed that the 3DS XL was only $169.99 on Amazon. I didn't realize it was a sale, but I found out this morning when I checked again and it was back up to $199.99. Turns out that Best Buy had a two-day sale to coincide with the release of the special Pokémon X and Y editions, so they discounted the console $30 (both the regular 3DS and the XL), and Amazon then matched their price on it.
I was going back and forth with myself yesterday on whether to go ahead and order it and X, but I thought to put it off some. I was kicking myself for missing the opportunity after I found out it was just a two-day sale (especially because I would have saved* an additional $10 or so if I'd ordered it from Amazon).
*technically; in reality it's that Amazon is one of the 5% earning categories this quarter for my credit card - but $210 = $10.50 in points. $10 from $210 is more valuable than $12 from $240.
My next best opportunity like this is probably going to be the Monday after Thanksgiving. Last year there was a $20 discount on the 3DS XL, so hopefully - knock on wood - something similar will happen this year too.