Trepidation

Meaning: Cotgrave: Trembling, terrour, feare.

Usefulness: 1 (As a friend pointed out recently, particularly useful as a description of how one feels while awaiting the arrival of a hangover; dread and trembling indeed.)

Logofascination: 1 (From shaking or trembling in PIE to alarmed or scared in Latin, through various shifts through both meanings in English, and with a diversion into the astronomical, the history of this word oscillates between the shaking and the scared. I sense it has swung toward scared of late, and possibly out into foreboding, but given its history, this may not last.)

Heliacal

Meaning: rising and setting with the sun - when applied to stars, those that rise just before or set just after the sun, since if they rise or set at exactly the same time you wouldn't be able to see the star.

Usefulness: 1 (Stars move through this cycle, which has allowed people to do various clever and useful things by tracking them.)

Logofascination: 2 (Heliacal means relating to the sun, and as etymonline points out, a heliacal year can also be a canicular year, thanks to our friend Sirius, the dog star.)

Bezazz

Meaning: it's an alternate spelling (and pronunciation?) of pizazz, which is one of the mysterious origin unknown words.

Usefulness: 2 (hipster points: if people correct you, you can look at them pityingly and remark that it's an early variant. Sounds a bit like bees knees, beeswax, and other such melittological slang; so much so that I find myself having to resist the temptation to etymologise folksily.)

Logofascination: 3 (only escapes boring by virtue of having z three times)