Ammonia.  This is an old school chemical that can really make light work of some difficult tasks, but there are cautions.  The first is to NEVER use with any other product containing bleach, the 2nd is to only use in a well-ventilated area.  Using the lemon-scented version will make it easier to work with, but there is no getting way from that odor entirely!  As with all chemicals ammonia works better when it’s been allowed to saturate the problem area.  15 minutes is usually fine when it comes to ammonia.

To clean an especially built up oven, try this no-scrub trick.  Heat the oven to 150 and then turn it off.  Place a small pan with 1 cup of ammonia on the top shelf and a large pan of boiling water on the bottom shelf.  Close the oven and allow it to sit for 12-24 hours depending on the amount of build-up.  You will need to thoroughly rinse the oven after this and if there is any debris remaining a bit of baking soda will most often erase that right away!

Safely clean all your jewelry (except pearls) with a solution of half ammonia and half water.  Get between the prongs with a toothbrush, then rinse and shine for that brand new look again.