Local Coop Games from the older PC Generation?

All LEGO games and some Resident evils :)

Worms!!! (How old?)

Little Fighters 2 and mods. We played the shit out of it back in the days :)

Metal Slug
Mortal Kombat Komplete (Arcade edition)

Portal 2
Borderlands 1 & 2 & 3
Heroes III
Civilization III / V
Worms Armageddon / WWP / WMD
Sven CoOp
Saints Row III / IV

p.s. can you describe what PC do you have? specs pls

A few ideas, jumping around time and genre a fair bit.

-Scorched Earth
-Worms
-Joust
-Rampage
-Contra
-some of the earlier 2D fighting games (street Fighter style but I can't think of early examples off hand)
-games like Double Dragon or Final Fight
-Wacky Wheels
-I seem to recall a simultaneous two-player Pac-Man knock-off but I have no idea what it was called.

I don't remember very well but maybe football manager and monaco has local coop.

Ironman Ivan Stewart's Super Off-Road
The Lost Vikings - Although apparently the first one on pc doesn't offer co-op
Qbasic - Gorillas
4D Boxing - Although couldn't find how to add the second player and it has passwords you need from the manual to play

As mentioned by others:
Worms
Rampage

There are probably others but those are some I remember.

Klomanager aka toilet tycoon (if you want to count that as coop)
Worms
Earth defense force. The console versions atleast offer coop, so i guess the pc versions do that either.
depends ofc what you understand as old. 2 years? 5? 10?