Do you want your students thinking differently about something they probably encounter every day?
Human body systems are taught at so many different grade levels. Students are often interested and excited as it relates to their own body, but they quickly can lose interest if the information is dry and repetitive. Here is one of my favorite labs. Be ready for some yelling and middle school excitement :). A great introduction to dissection, in a pretty tame way.
Here is a video clip from youtube: (not mine)