Without the Harrier, the UK would have been obliged to retain a proper carrier or two, and the Falklands would have been won easily, or never started.
Most significant aircraft were the ones that ensured the Cold War stayed Cold - Vulcan and Phantom, latterly Tornado.
Even more significant was the level of effort by the personnel - all Ranks, Trades and Branches, to ensure readiness. All those Tacevals were worth it, as post-Soviet analysis of WarPac readiness/capability is showing. NATO would have won.