The 26-year-old has played in all eight of his club's European fixtures this season, claiming a crucial try in the Heineken Cup win over Saracens in November before bagging a sensational hat-trick in the convincing defeat of the Ospreys three-and-a-half months ago.
And while Toulon may start the Amlin showpiece as slight favourites due to their better league form and the nature of their star-studded squad, Ngwenya's presence in the Biarritz line up means even the slightest of slip ups is likely to be punished.
The possibility of Ngwenya racing down the touchline for the winning score at The Stoop next week got us all reminiscing about one of the most famous individual scores in the history of the Heineken Cup - the day the US international whizzed past by Williams on an 80-metre dash to the line at the Parc des Sports Aguilera as Biarritz edged past the Ospreys in April 2010.
Having been given a chance to attack the former IRB World Player of the Year for on the blindside of a Biarritz scrum in his own 22, Ngwenya first fended him off and then showed him a clean pair of heels to set the entire stadium buzzing and the whole of Europe talking.
It was breathtaking stuff and it added to 'Taku's' growing reputation as a finisher after he embarrassed Springbok legend Habana at the 2007 Rugby World Cup with a devastating turn of touchline speed.
Looking back to the decisive moment in that thrilling Heineken Cup quarter-final two years ago got us thinking - who is the fastest man to have played rugby union? In recent times, the Cardiff and Wales wing Nigel Walker has a claim to being one of the quickest of all time.
Walker featured for Cardiff against Toulouse in the inaugural Heineken Cup final in 1996 and was an athlete before returning to rugby. An Olympic sprint hurdles semi-finalist, his best legal track time over 100 metres was 10.47 sec with a wind assisted figure of 10.34 sec as his fastest flat run.
He trained with the likes of Olympic 100 metre champion Linford Christie and double World 110 hurdles champion and world record holder Colin Jackson during his track career before carving out a 17 Test, 12 try rugby record with Wales.
Walker certainly knew his way to the try line but he is convinced that Ngwenya is his nearest rival when it comes to the current crop of speedsters.
"Bryan Habana is very quick, but I wouldn't rate him as fast as Ngwenya. If there were a race between the two my money would certainly be on Ngwenya," said Walker.
"What Ngwenya demonstrated with that try against Shane Williams is not only does he have explosive speed over the short distance, but he can also maintain it over a longer sprint. It's all very well having an impressive 100 metre time as a rugby player, but how often do you get the chance to run that distance in a game?
"In rugby it is all about the first 15-30 metres and getting away from people and that's where Shane excels. You often find that the athletes who are short are the fastest because they can accelerate quicker that anyone else.
"It is about your explosive strength in the first instance and then about your ability to sustain your speed over a longer distance. When I was running at the major championships I used to train with Linford Christie and Colin Jackson over 30 and 40 metres. I would stay with them over 30 metres, and often beat them, because I was good out of the blocks.
"But from 32-40 metres I would invariably find Linford coasting past me and leaving me almost standing. It is hard to understand just how fast someone has to run to break the 10.00 seconds barrier over 100 metres.
"You are never going to be as fast on a rugby field as you are on the track, but speed can still be a major asset. If you come down from a top 100 metre speed of 10.4 sec on the track to even 11.0 sec on a rugby field, you are still going to be much faster than the majority of players.
"The quickest players I came up against were the All Blacks pair of Jeff Wilson and Christian Cullen. Ieuan Evans was sharp over 20-30 metres and had a wonderful rugby brain as well.
"The French wing Patrice Lagisquet was always rapid, but the quickest man I think I've ever seen on a rugby field was the former Wales and Lions wing JJ Williams. He had a track time of 10.4 sec, which is very quick, and he transferred that pace on to the pitch."