מבטל כלי מהיכנו (nullifying a vessel from its normal usage). Putting a כלי (utensil/vessel) under candles to catch oil, to catch the candle and...
Cutting and eating all other types of fruits (e.g. oranges, grapefruits, cherries) and what to do with the leftover juices.
is one allowed to use a plunger on Shabbos;