Jacuzzi
The name Jacuzzi is a trademark name for whirlpool/spa/hot tub/etc.
jelly, jello or Jell-O?
In British English (and throughout the rest of the Commonwealth) jelly is the name of the wobbly dessert. In the US, this same dessert is called jello. The spelling Jell-O should be reserved for the trademark brand. Jelly in US English means a particular type of thin jam (often without seeds).
jewellery or jewelry, jeweller or jeweler?
The standard spellings are jewellery in British English and jewelry in US English. The same difference applies to jeweller (UK) and jeweler (US). Jewelry is the older spelling and it may surprise people that the newer spelling, jewellery, only appeared in the 1900s. Fowler condemned this newer spelling as both "commercial" and "popular". Canadian spelling fluctuates between the two in equal measure and Australians use the "British" spelling jewellery. Both Canadian and Australian English write jeweller. The word jewel comes from Old French joel, which derives from jeu (meaning "game or play") and itself comes from Latin jocus ("jest").
jimmy or jemmy?
The spelling is jemmy is the US and Canada, and jimmy in Britain and Australia.
judgement or judgment?
The preferred British spelling is actually with an -e-, though it often appears without it. The only American form is judgment, whereas the British variants do differ in usage. Judgement is the common spelling and judgment only applies to final decisions made made by a judge. This distinction is not made in American English, which seems to have crept into ever increasing usage also in the UK.
judgement call
By all means, make a judgement, but there is no need to add another word to it.
just deserts
The phrase just deserts is spelt with one only one s, unless you are skipping the main meal and only having dessert.
