I wouldn't try the Farmers with sandbags. They'll be bouncing off your legs and screw with your footing. Now, overhead sandbag walks could be a fun animal.
You might want to try a stone/sandbag zigzag carry. 6 steps one way, 6 steps diagonally the other way in a zig-zag pattern. It really reminds you of that you have abs, obliques, and ankles. But don't try to turn too faast, or it'll be an easy way to twist a knee.
Also, Tabata sled sprints would be a hardcore choice. But having it in a medley might be too rough.
You always have a good old fashioned car push. That's 2 tons of fun, just waiting for you.