Most of my time in my Melee days was spent on Hyrule Castle against CPUs because I love seeing everyone go flying everywhere. Generally did 2v2 teams to keep things a bit more chaotic and interesting. Marth + Roy vs Link and Young Link were usually the teams because I loved hearing the swords clash and Marth + Link were basically my mains. For the longest time I couldn't tell who was my main, it took years before I figured it was Marth.... However later on I kinda figured that it was because back in my melee days projectiles didn't feel that useful, and Marth's range made him pretty easy to hit the CPUs safely. Was going to get good in later Smash games, then try to go back to Melee and see how vastly different it'll feel.
There aren't many good players in my town, so the occasional 3 v 1 was a really fun time for the first few matches of whatever day I play. Of course, played on Hyrule castle though, it was literally everyone's favorite stage when they came over to play Melee.
Then there was the time where a friend of mine who hates to lose deciding to have me fight against 2 level 9 computers and him. He basically had an imaginary line on the stage so I couldn't go past him or he would attack me. Which can be difficult when you're trying to fight 2 other combatants. It was a very difficult match. =
Lastly, fighting against a Mario main. I was a Marth main, so I won every time but it was close-ish. Then eventually we swapped and he won with Marth but it was still closeish. Of course he never played Marth and I never played Mario. I do think Mario is a bit harder to use than Marth as well. I always wanted to play more against him, but it would be so many years until I met a Pikachu main in Smash 4 where I found someone around my skill level. Perhaps I'll find another person to fight in Melee again.