Conundrum
Puzzle, mystery
Vestige
Sign, trace
Encumbrance
Stress, obligation
Recalcitrant
Awkward, difficult
Construe
Read, analyse
Maverick
Rebel, outsider
Garrulous
Chattering, talkative
Noisome
Nasty, disagreeable
Galvanizing
Startling, shocking
Relegate
Exile, banish
Penurious
Needy, poor
Neophyte
Learner, novice
Exacerbate
Increase, worsen
Demur
Protest
Anomaly
Variation, rarity