I always knew Meta Knight was the best, because his nades cover a ridiculous amount of space, he can cover a lot of ground with other moves, his up B was hard to punish early on, his side B was annoyingly good, he had several early kill moves, and he was one of the only characters that could almost always land extra hits after the first hit (lol combos).
I figured Marth was right below him because he was just an all-around threat, and Snake was probably tied with Marth (if not better) because he has ridiculous range, early on outcamped everyone but ROB, and seemed to have the most potential for improvement. Plus those early techniques... were ridiculous.
I figured Fox and especially Diddy Kong were definitely high tier characters long before they were high tier on the tiers, too. I am still shocked about how good Diddy Kong is. I never saw him being that good, even though I thought he could be a dominate character.
I also figured ROB would become weaker (initially some people thought he was top tier). I didn't think he would sink to his low/mid tier position he is now. I'm glad the ROB camping fest ending, because that crap was bound to die; and if it didn't, Brawl would be as competitively active as Soul Calibur 3. I'm glad that campy ROB 12 minute matches crap died. I like how the people who played ROB that lame campy way mostly quit or became obscure because they had little talent outside of camping, lulz.
Seeing as how I knew my main would be Toon Link since before day 1, I figured he would be slightly above average in Brawl before I even saw him based on how his style would play out. The first time I played him I faced my friend MM (who usually beat me) on Wifi in a 3 stock match... and 3 stocked him... without taking damage. I have video evidence, lol! I knew then he would be high mid tier or high tier for sure. Pretty much from the get go we all knew what he was capable of.
The character that really shocked me was Donkey Kong. I thought he sucked balls initially, even worse than in Smash 64 and Melee, and I was positive he would be at or very close to the very bottom. Well, apparently the jokes on me.