The stock market has daily risers and fallers. It's an actual metric that is used to gauge the overall up or down direction of the market. In TF2, it's not exactly the same but there are certainly items that rise and fall. Newer items tend to start out strong and fall with time. However that isn't always the case, as we see currently with Essential Accessories which are a continually popular item and have risen in price recently.
Other items of note are the Salvaged Crate #30 items. There is a real sense of scarcity to the more popular of these strange items (Machina, Kritzkrieg) that even carries over to the Gunslinger. Mackerel and Caber have a little bump, but there are still plenty of sellers at their respectively lower prices. Crate #30 continues to be kept in short supply.
Keys are slowly becoming more available this weekend. Many traders who bought at 2 refined and 2 reclaimed will not be thrilled to know that the high prices they paid will likely soon bring the price back to equilibrium. Keys are starting (slowly) to sell again for 2.44 and 2.33 refined...although this is not the official price yet as the influx of keys could be temporary.
Newer genuine items from the Saints Row promo are now tradeable and sell as a set (mostly) for around Bills Hat in price. This is considered a lower price for a set of new genuines so the game must have sold well or was considered cheap by buyers. Football Manager items have a strong price range around buds for the set. Trine 2 and Assassin's Creed items are not yet tradeable. The heavy hat for Trine 2 is a love/hate item apparently. Assasin's Creed items look to be popular, although they are only for the spy which will be interesting to see if they trade for high value.
The Halloween items have quieted considerably as it would be expected. The prices for them will likely fall (if not already) and we will adjust as we see how they sell. They are not a typical item being they are usable only 3 days about per month and on Halloween events. Buy them on the cheap only is our suggestion. ("scrap -" means a scrap maximum per item).