Sharpen the blade twice each season to help maintain a green, healthy lawn. A sharp blade not only cuts blades clean so grass plants recover quickly, it helps reduce your lawn mowing time. Learn how to sharpen your lawn mower blade at http://www.familyhandyman.com/DIY-Projects/Outdoor-Projects/Yard/Lawnmowers/lawn-mower-blade-sharpening
Lawnmower blade improvised weapon idea. ((In the genre of converting tools into knives, I like this the most, because in a real disaster, you're just going to buy a new lawn mower later, right? Or gut the engine for parts.))
Cute idea for drainage! Use flat pavers along driveway edge, a water pathway of stone with black cloth underneath, rough organic looking pavers like these along grass edge. Keep the the pavers level with the ground so the lawn mower blades will not hit. This also means digging the water pathway lower than the paver path.