Plants in the wild can be a great source of food or a death sentence, mushrooms are by far the most dangerous due to how toxic they can be and how hard some can be to identify, though there are some super easy ones depending on your area. For the sake of safety, I will not show or mention kinds of edible mushrooms, I recommend finding a local mushroom hunter if you are interested in them. With that out of the way let get into my personal favorites.
This is yellow wood sorrel.
This small clover-looking plant is very easy to identify and as far as I know, does not have any poisonous look-alike.
It has a very sweet/sour taste and is full of vitamins, you can eat it raw or use it to add some flavor to whatever you are cooking. Due to the sweet almost citrus like taste, I prefer it will fish, but it also goes well with other wild edible plants that don't taste as good.
Dandelions are often just seen as weeds with no real use, but they are packed full of vitamins and even have some decent carbohydrates and a little protein as well.
Then entire plant is edible though some of it is very bitter depending on age. The young leaves are great in salad, the flowers make a good tea and are a tasty treat fried with a little butter, the roots can be made into a pretty good tea as well and acts as a diuretic. Many of these plants do have some form of medicinal uses (I am not a doctor and this information has not been reviewed by any doctor if you are trying to treat an illness consult your doctor)
Cattails are a great source of food and can also be used for other purposes such as fire starter.
Like the other plants I have mentioned the entire plant is edible at the right time of year. The brown part is not edible after it has matured but when it is young can be cooked up and eaten like corn on the cob, if it is too late then you get a mouth full of fluff that is just not fun (funny to do to a friend though) the leaves can be cooked up like spinach when they are young but as they get older they do get pretty tough and woody though you can still eat the lower tender bit of them. The roots and lower part of the stalk are great raw or cooked and are full of
Wild berries are a great food as well but be careful to know what you are looking at as there are many poisonous types.
Raspberries and blackberries are the easiest to identify and are also the best eating in my opinion, they are absolutely delicious and nutritious and the leaves can be used to make a healthy, tasty tea. Unfortunately, they have a very short season so they are not a reliable source of food for the long term or if you are looking at the wrong times of the year.
Common clover. While not tasting the best it is not bad and the entire plant is also edible.
While looking very similar to wood sorrel they do not taste anything alike. The flower of clover plants are the best part in my opinion and again make a good tea (I enjoy tea if you can't tell) the green are great to eat raw as a salad and while they are not much for calories they do have plenty of vitamins and usually grow in large patches so you can gather a lot of them at one time.
These are just a few of my favorite wild edibles that you really can't get mixed up and accidentally poison yourself with. If you would like to learn more I recommend the National Audubon society book on wild flowers.