Although Inzamam-Ul-Haq essentially failed in subsequent World Cup tournaments (an 81 against Australia at Leeds in the 1999 World Cup aside), I think his blitzkrieg innings of 60 ranks highly amongst the supreme under-pressure World Cup knocks.
Coming in with the score at 140/4 in the 35th over, he stroked the ball nonchalantly during his wonderful knock, in the windy conditions present at the ground at that memorable day. Producing a partnership of 87 with Javed Miandad, he allowed Pakistan to reach the finals of the tournament from a seemingly unfathomable position; I very much doubt obtaining 123 in the last 15 overs was possible way back in 1992.
And all of that in a World Cup semi-final too! In the rest of the tournament he failed to perform (apart from in the final against England - where he scored 35 (42) - and the game against South Africa - where he looked good until he was dismissed by the infamous Jonty Rhodes 'superman run out' for a score of 48 (44) and so it is inevitable that the pressure must have been upon him too.
In fact, Imran Khan was really the only senior player who truly believed in his abilities (Inzamam himself was reluctant to play because of a stomach bug suffered a few days before the match, if I'm not mistaken) - if I recall correctly, after Salim Malik was out for a meagre score of 1, Javed Miandad signaled to the dressing room to send out Wasim Akram to bat (suggesting his lack of faith in Inzy's capabilities). Thankfully, Imran Khan was still Pakistan's captain until the conclusion of the 1992 World Cup - otherwise, we may never have seen the elegant stroke-player of Inzamam-Ul-Haq and witnessed some of cricket's greatest innings.
Here is the scorecard of the match:
Here is some footage of the innings:
Inzamam-ul-Haq vs. Newzealand in 1992 World Cup - Vidpk.com
Apologies for the absence of a YouTube link - I searched hard for one but they all seem to have been removed.