Here are ten of mine in no particular order - love to hear yours. 
Some weird Vasectomy game on the ZX81
Playing Chuckie Egg and Mr Do on the BBC B from Blockbusters at tea time to sunrise the next morning.
Moon Cresta in the arcade at Walthamstow market.
The buzz surrounding SFII on Jap import for the SFC.
The joy of 'discovering' the Japan Saturn.
Realising how the internet had shrunk the world upon receiving parcels of secondhand games from Asia.
Each week a different SNES game game rented from Colin at Megaware (what happened to him?).
Buying virtually all Colin's stock of SNES rental games when the Playstation took off.
Taking the plunge to pay a ridiculous amount for the SNES Starfox Japanese import.
That special Retro edition of Edge magazine that re-kindled all the love for this stuff.
Some weird Vasectomy game on the ZX81
Playing Chuckie Egg and Mr Do on the BBC B from Blockbusters at tea time to sunrise the next morning.
Moon Cresta in the arcade at Walthamstow market.
The buzz surrounding SFII on Jap import for the SFC.
The joy of 'discovering' the Japan Saturn.
Realising how the internet had shrunk the world upon receiving parcels of secondhand games from Asia.
Each week a different SNES game game rented from Colin at Megaware (what happened to him?).
Buying virtually all Colin's stock of SNES rental games when the Playstation took off.
Taking the plunge to pay a ridiculous amount for the SNES Starfox Japanese import.
That special Retro edition of Edge magazine that re-kindled all the love for this stuff.