Here's a few. I have my father to thank for most of these.
Quake
What can I say? It's Quake. Extremely memorable game.
Crusader: No Remorse
I remember plating this quite a bit until my mum snapped the disc because she accused it of making my brother and I violent with each other. This was before I managed to get her to see video games in a better light.
Theme Hospital
I loved this one. It was very challenging for me at the time, but my dad and I would always laugh at the ridiculous diseases. My favourite was bloaty head syndrome.
Fatal Racing
This is a fairly obscure but fun one. Crazy racing game with corkscrews, massive jumps, and exploding cars.
Caesar III
To this day, still one of my favourite city builders. Very deep, complex, and challenging. I always got really jealous of the cities that my dad was able to make. I've gotten better since then, but it's still pretty difficult.
Worms Armageddon
Still the best Worms game ever made. I still play it online sometimes. I also used to play it with my friends on the shitty computers in the computer lab after school.
Dune II
Another one that my dad and I loved.