Pencil / Colored Pencil

pros:

they are easily accsessable
they blend very easily
they are much than other materials
there are many different types, if you do not like the type you are using, you can use another brand!
you can erase they don't dry out

Cons:

They can also be very expensive
they are easy to lose and break
they can smuge
you have to resharpen
they can smudge other used media