I think Lagoon may have passed me by and I never played many PC games.
Mario Kart 64 though was fantastic. I don't think there is any Mario Kart released since then that matches it. Hours of fun with mates (although you needed a pretty big TV to make four-player enjoyable) and one of my favourite N64 games. It still doesn't quite surpass the original Super Mario Kart for me (though many will disagree) as the course diversity and level of control in the original was perfect.