Wales' record try-scorer bagged a brace of tries in the drubbing of the Pumas in Cardiff.
The landmark strike at the Millennium Stadium puts Williams ahead of All Blacks great Doug Howlett and into joint-third place alongside former England flying wing Rory Underwood on the all-time try-scoring list.
But Williams, who has struck 48 times for Wales and twice for the British & Irish Lions, insists there is plenty more to come.
"It's a great honour and I'm really pleased to score 50 tries," said Williams.
"It will be great to tell the children and grandchildren when I hang the boots up but I am just as happy when I scored my first try for Wales.
"The accolade of scoring the number of tries is just a bonus to me and I won't let the feat affect me. I never expected it would happen and it still feels mad. I don't want to get carried away because I feel there is more tries in me.
"Hopefully I get picked to face Australia next weekend and if I score to become the greatest in the northern hemisphere, then I'll be a happy man."
Only Japan's Daisuke Ohata with 69 tries and Australian legend David Campese stand in the way of Williams becoming the greatest finisher of all-time.
And the 32-year-old current IRB World Player of the Year admits he has Campese, on 64 touchdowns, in his sights ahead of the mouth-watering clash with the Wallabies next Saturday.
"When you look back in history to the likes of Campese, it's a massive honour for me to be mentioned alongside quality players like him," added Williams.
"I'm still enjoying my rugby and believe I'm capable of scoring even more - it's my job.
"I want to get up to David Campese one day and I hope number 50 wasn't the last of my tries. I want people to be talking about my 51st and 52nd tries and so on."
World's top 10 try-scorers
1. Daisuke Ohata (Japan); Caps - 58; Tries - 69
2. David Campese (Australia); 101; 64
3. Rory Underwood (England and British & Irish Lions); 91; 50
Shane Williams (Wales and British & Irish Lions); 71; 50
5. Doug Howlett (New Zealand); 62; 49
6. Christian Cullen (New Zealand) 58; 46
7. Joe Rokocoko (New Zealand); 60; 45
8. Jeff Wilson (New Zealand) 60; 44
9. Gareth Thomas (Wales and British & Irish Lions); 103; 41
10. Chris Latham (Australia); 77; 40
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