A few pieces of kit that i think are great and help to add variety to the sessions;
Crazy catch - great for within a fielding circuit and when taken apart great for short leg / silly point work
Baseball mitts - helps to break groups down into smaller numbers - i think theres nothing worse in pre season than waiting a couple of minutes in between each catch!
Fusion Stumps - great for pre match warm ups as the ball doesnt deflect so much when the bowlers hit it and lots of catching drills can be down with them too
Half bats - some great half bats from red ink cricket at the proper weights rather than the cheap ones form the major brands
3oz bowling machine balls - great for bback foot work and also batting against swing. Also bit of fun in fielding drills
Tennis balls - regardless of level great for doing batting drills
Cones - very basic but having plenty means you can set up multiple fielding drills in advance rather than waiting between each different drill