Both of these ideas came from nothing more than general ideas bouncing around in my head that triggered the 'That might make a good SCP' braincells.
First off, the Teddy Ruxpin. As with most electronic devices, it behaves a bit oddly when it's starting to run low on batteries - aided by the fact that the original model uses regular audio cassette tapes. So why not have one that is -extra- creepy when it's low on batteries?
To facilitate that, give it a disturbing effect on children who listen to it for long periods of time - homicidal tendencies, disturbing thoughts, generally turning them into miniature serial killers. It can run perpetually when the batteries are low instead of eventually stopping, and if it is destroyed, re-appears nearby undamaged (though still showing its normal signs of wear-and-tear). The slow, slurred speech can be unintelligible to adults, but fascinating to children, who will also after enough exposure grow very attached to the object, with an effective time similar to modern brainwashing techniques. This would, unfortunately, preclude a testing log; the D-class personnel are never children.
Second idea - the killer tree. I thought of this while eating a nectarine and looking at the pit, considering how the human body is so poorly suited for eating the pit (see: appendicitis). How about a tree that grows a small number of fruits that are delicious, with deadly seeds? Limit the number of fruits due to the complexity and exotic materials that would be needed to grow them, as well as to prevent needing an explanation as to why there isn't a survival instinct for everything in the area to not eat the darn things. The exceptionally hard seeds, when ingested accidentally while eating the incredibly succulent summer fruit, will activate upon coming into contact with stomach acid - bonding to the stomach wall. Chemicals are released that cause the victim to feel exceptionally cold and sleepy, preferably (for the fruit) making the host find a sunny spot and sleep there. And then the high dose of arsenic in the seed (because a lot of seeds have arsenic - apple seeds in particular) kills the host. Quickly sprouting while making use of the body's readily-available nutrients, especially once the stomach wall is ruptured - allowing the body to partially digest itself - the corpse will eventually have a sapling that is rooted to the ground and sprouting through the chest cavity of the host body, where it will continue to fertilize the ground and provide for a boost to the tree's growth. No additional carnivorous traits are present until, three years later, the first fruits grow on the branches of the tree.
Do either of those sound too cliche/terrible to live, or shall I put together sandboxes for 'em both?