I have learned to pronounce it like you spell it, sounds like Tipp-ex but then just with the “K”
There is definitely an ‘n’ in there right after the “K” 
Knipex
That’s the K sorted out but what about the P?
Is it P as in Pea or Peck?
Love these tools, and have several. I always pronounced it nipex, but most of the time pronounce it pliers.
It’s knee with a k and pex
You pronounce it “Pass me the damn Pliers” 
Poorly
It’s Cnippex.
ex•pen•sive
Jamie says Nye-Pex at 5:30.
Busted! I believe our German friend. After all, these are tools made in Germany.
I've been pronouncing it wrong since the mid 90s when the company I worked for first started selling their tools. It'll always be Nippex to me. :)
kuh-Nee-pex is how the company itself pronounces it. kuh-Nip-ex is the accepted form for foreigners.
They need to produce a flashlight....
Hmm...browsed by their youtube to see what was new besides their Engineer screw pliers ripoff, and listening to this company manager he makes it sound like "keepex"...what the heck.
0:51 to 1:06 he says it twice: https://www.youtube.com/watch?v=YfZwJ3_f1WQ
Engineer 8” plier = best plier 
They make fantastic nippers and strippers, too. Actually prefer them over many others although the small Knipex flush cutters I have are great. I don't know why Engineer hasn't ever caught on more than it has in the US.
I pronounce it Irwin because I find the quality close enough and the price much better. Just, I own a couple Knipex pliers. Bought my Dad a nice set of 3.
I say it like knife…
Nigh-pecks
Nip-Ex, and I’m from the USA. I’ve honestly never heard it pronounced any other way.
I think I’m in love with the pliers wrench XS! Have some of the bigger variants and they are amazing. Most Knipex products are worth their price. If you use them within their specs they will hold forever.
They are a bit overrated.
I mean, the tools are good, but there’s really not much difference compared to cheap tools as the online propaganda tries to assert.
If you abuse them, they will fail too.
I like their pliers wrench, it’s one of the most useful tools and you cannot find it at other brands because Knipex holds the patent.
I slightly bent mine when hammering it to loose a nut 
KnipFire.