Mistletoe
Harmless if you eat a couple berries,but if a ton is eaten it can start to cause some damage such as cramps,"water chocolate" (You should know what i mean),and convulsions. If you eat the leaves you will start to feel the effects sooner.
Jerusalem berries.
If you eat four or more berries it may cause you to throw up,can be used as yarrow if one ate something bad.