I gotta say Cantillon Gueuze is a step in the deep end.
Even compared to other unsweetened lambics, it's very sour in comparison. Possibly not as funky as some i've come across, like Hanssens or Oude Beersel, who tend to have a more prominant stinky "horse" component about them, but I found Cantillon an absolute sour menace on the palate...in a good way.
The first Gueuzes' I ever came across were the sweeter, big name ones; Lindemans, Timmermans, Mort Subtile, Belle Vue. Less sour, less funk, but still interesting beers...like comparing the tartness of natural yoghurt to grapefruit rind.