Using Ramon Martinez of the Boston Red Sox, use the 4th pitch key ('S' on the keyboard), even though he only has three pitches listed. He will throw a sadistic curveball at 107 MPH, every time. I do not think this affects his fatigue any more than your average fastball.
Secret Teams
Click on Help and then About Baseball 2000. Now, on the first occurance of Wizbang, right click the mouse twice. It's on the 2nd line of the Copyright Declaration. Do that and you will be awarded a Special Team.
Special Teams
Microsoft - Play with guys at Microsoft.
Wizbang - Developers in Ball Uniforms (including women).
Robots - No squeaky hinges.
Training mode
Press [Ctrl] + T to practice pitching and fielding.
View programmer baseball card
Press 'S' to have the batter spit. Keep pressing it until the programmer baseball cards appear.