Mine Cart- There are minecarts around the whole map, simply kick or leash a mine cart to kill a guy. Skill shot I think is called "Railed"
Oven- There is a huge furnace at the back of the map, simply kick or leash a guy into the oven. Skill shot is called "Man Toast"
Fan- Next to the oven or furnace are two large fans. Kick or leash a guy into them, called Blood Bath.
Smasher- Go right immediatly and you will be next to some boxes on a metal walkway. Next to some buildings off of the map you will see two or three giant cogs attached to a crane like system. Simply kick a guy around the cogs and they will smash him. This is called "Man Crush."
Lava Cart- To your left when you spawn you will see a hanging cart that you can leash. There are three of them on the map. Get a guy underneath it and leash the cart which will drop lava on the guy. This is called "Golden Shower."
Doing all of these in one wave will net you the environmentalist achievement. You should get it right away after you finish the last one. Good luck
Edit: Thanks to TBonePhone for giving me more of the names of the skill shots