Sound test:
Hold L + R at the title screen.

Hall of Famers:
Win three consecutive Super Bowls with the same team, then immediately enter the next season with the trade mode enabled. Various players from the Hall of Fame will be in the agent pool.

Extra player creation points:
Enter the player creation screen and view how many power lines have been assigned to a player. Leave that player incomplete if not enough lines are present. Repeat this several times until the player has three or more full power lines.