Probably my first solo out of the circuit - flying along the coast at 4000 feet with perfect blue sky and unlimited visibility was wonderful after hours of circuit bashing. The first solo navex was also memorable, but on the first local solo there was nothing to do but look out of the window and enjoy. On the navex the workload got in the way a bit
Another good'un was sitting on the wing of a PA-28 at Bournemouth after the first leg of my QXC, watching the the Red Arrows run and break overhead, land, taxi past and park up just across the grass from me
(hearing the tower say "Ryanair xxx, follow the PA-28 to..." as I was departing was kind of cool too
)
D'oh - the title says "what's the one, absolute highlight..." and I've put two