What's the first lens that made you say "Wow"

Crop 17-55 2.8

FF 70-200 f4 Lis

I feel like I do this with every new lens I buy... but the one that really sticks out in my head is my first macro lens, 100mm f/2.8 non-L. I had never seen any of my pictures turn out so sharp.

The sigma 30 f/1.4. I used it almost exclusively on my 1D for over a year.

300mm / 2.8

Definitely the Canon EF 100mm f/2.8 Macro. At the time I only had the 18-55 and 55-250 kit lenses for my Rebel XSi. The macro lens was so significantly better in every aspect. I was an idiot and ended up selling it. Once I went full frame I really missed it, so I got the L IS version. It is every bit as good as the older version of the lens. The IS makes field macro much easier and makes it much more useful for general photography.

50mm f/1.2L

I use it so much Im almost to the point of welding it to my 5DIII.

For me the Sigma 17-70 f/2.8-4 Macro. It was the first lens I bought to replace my kit lens and it totally had that WOW factor for me. So much so, I still own it and it pretty much lives on my 60D.

200L F2 IS.

Originally it was my 85 1.8, then i got the 100mm F2.8 macro an that changed my mind

35L. Still makes me say "wow" everytime I use it.

The 85L ... Now that lens makes me speechless

The Canon 70-200 4.0 L. It's just a super sharp lens.

For me, the sigma 17-50 because it was my first "real" lens as far as IQ, faster constant aperture and build and feel. I had a 50 1.8 at the time, but that sigma was like wow coming from the kit. I don't think I will ever sell it as long as I still have a crop body.

Not the first time obviously after what I stated above, but the only other time (it is harder and harder to say wow as you go along) was recently with a 24Lii. It has pretty much been glued to my 6d and I am elated with it. My favorite lens ever so far.

Yashica 135 f/2.8 MLc.
Oh! You mean within the last 30 years? In that case, EF 35mm f/2 IS USM.

Hasselblad 80mm Planar

In this chronological order of acquisition

Canon 50mm f/1.8
Sigma 30mm f/1.4
Canon 135mm f/2 L
Canon 70-200mm f/2.8 IS II L
Sigma 50mm f/1.4
Canon 100mm f/2
Canon 17-40mm f/4 L