Super Smash Bros. (64) in competitive play
From SmashWiki, the Super Smash Bros. wiki
The original Super Smash Bros. getting competitive play did not start at the initial release of the game, unlike all of its successors. In fact, the first Smash Bros. did not develop almost any community at all until Melee came along two years later as a breakout sequel. Only then did the newborn Smash tournament scene have small groups of people take a second look at the 64 version.
The first offline Smash 64 tournament that could be considered a national was FC Diamond, held in 2007, because it featured a larger than normal influx of players and spectators alike.