Well I never kept a list so I'm missing like 90% of the oldschool gems but I'm just going to name some that I remember.
https://www.epicwar.com/maps/43659/ Zombie Arena. It's tiny and simple.
https://www.epicwar.com/maps/107023/ Zombie Survival Xtreme 2.7. Like Kodo Tag.
https://www.epicwar.com/maps/11973/ Arcade Zombie Survival. Warning kind of bores me, especially after first time playing.
https://www.epicwar.com/maps/1611/ Soldier TD. A simple TD.
https://www.epicwar.com/maps/99960/ Nintendo TD. A simple Nintendo TD (sometimes desync). I like it though.
https://www.epicwar.com/maps/74160/ Protect the Guy. Simple TD-like game.
https://www.epicwar.com/maps/64469/ Protect the Queen. Warning though, unbalanced + really tough game.
https://www.epicwar.com/maps/86226/ Protect the House. Fun and simple. There are newer versions which ruin the fun/simplicity.
https://www.epicwar.com/maps/123679/ Fortress Survival 4.80. Very old and simple version compared to overly complicated nowadays. Warning potentially long game.
https://www.epicwar.com/maps/2/ Spiral TD Survivor. Old and simple.
https://www.epicwar.com/maps/22889/ Random Unit. There are a lot of versions, I'm only linking the oldest one. Require 5-8 players for max fun.
https://www.epicwar.com/maps/314/ Art of Defence. Kind of wc3 melee style game but fun.
https://www.epicwar.com/maps/6423/ Cube Defence. Epic oldschool TD. Fun.
https://www.epicwar.com/maps/144327/ Super Labyrinth TD. Old but cool. Tough though. Teamwork needed.
https://www.epicwar.com/maps/120561/ Hoihoi Custom Hero Survival. Good stuff.
https://www.epicwar.com/maps/145215/ Custom Hero Arena Defense. Variation of above.
https://www.epicwar.com/maps/22588/ Hungry Hungry Felhounds. Needs multiple players. Minigame.
https://www.epicwar.com/maps/125974/ Are You a Lucker? Hilarious.
https://www.epicwar.com/maps/127319/ Toy Soldiers. Simple shooter game.