From Thassas Oracle to Armageddon, theres a lot to talk about
In Duel and Multiplayer modes, the game allowed a player to construct his or her own deck (using a specialized Deck Editor), or to play with a randomly generated deck (simulating a "fresh pack of cards" as was the custom in various tournaments at the time)
For example, if it has three +1/+1 counters on it and has been dealt 1 damage this turn, it will be destroyed immediately after you activate the ability a second time and you won't be able to activate it a third time
For the purposes keeping the summary below a manageable length, Im ignoring special subset cards (e.g., the Arceus inserts from the Arceus expansion, Radiant collection from Legendary Treasures, the unown subset from the ex Unseen Forces expansion) and mini-sets like Dragon Vault and Double Crisis
You can certainly go infinite with any creature that can produce more than four mana
Instead, it serves best as the premium commander for wall-tribal decks