Hard to choose. I'm particularly fond of the names of some of my Belgian ancestors, they are real mouthfuls: especially Van Weirelyckhuysen and Van Niewenhuysen (those two were a married couple).
I'm choosing Catherine Van Nereaux, a 4xg grandmother, as her name puzzled me for a while. Where could such an odd mixture of Dutch (Van XXX) and French (the second part is sometimes spelled "Néreaux") come from?
Catherine was born in Antwerp in 1798. Her father was a chemist, or apothecary, or perfume maker - those professions were almost interchangeable at the time, and her mother the daughter of a butcher. Catherine had two younger brothers, who apparently died young, and her father also died, when she was just 5 years old. However her mother managed to marry a noble - the groom's parents refused their consent ! I'm not sure how Catherine was raised. I'm afraid she was not a happy woman.
When she was 20 she married Lucas Dronkers-Martens (another interesting name) who was a sort of employee or civil servant. They had 13 children, including one she apparently abandoned at birth, and who was raised as "child of the Nation". Her consent was asked when her estranged son wished to get married, and she refused to acknowledge him even them. Only 4 of the remaining 12 children made it to adulthood.
And her name? Well, after thinking I'd never find, the baptism record of one of Catherine's uncles was found. Turns out her grandfather was really Etienne Vannereau, born in the early 1720s in Burgundy. Somehow the name was "Dutchified" by separating the Van from the rest, but they kept a decidedly French spelling. I guess they were probably still aware of their French origins after several generations. Etienne is still a brick wall - his parish of origin has no surviving records from the time he was born - and why he moved from the heart of France to Antwerp remains a mystery.
(This is not complete yet - at least her grandfather and her mother should be added).