My first on my own ZX Spectrum 48K was the games that came with it, Hungry Horace, Space Raiders and through the wall.
Later classics were Manic Miner, Chequered Flag, Jet Pac, Scuba Dive, Ants (I think this was the first proper 3D game ever), Sabre Wulf and Underwurlde (best of all platform games). These were the days...