Zoom technology has come a long way since the terrible examples of the 70s, 80s and early 90s. Canon's 17-40mm f4L zoom, bought speculatively given my preference for primes, is a gem, though a very hard one to master at 17mm. The extreme wide angle means key elements are placed further away than often desired, and distortion is very noticeable of horizontals. It redeems itself well in overall, edge to edge sharpness, just a bit too wide to be practical. My other favourite is an old EF 20mm f2.8 prime that, 22 years after purchase, is still a much-loved member of my 35mm kit.
In medium format my favourite is an ultra-wide 45mm.