Personally, I don't think running onto the field during a sporting event is ever a terrible idea—particularly during a baseball game. It entertains the fans and is a nice change of pace from the four hours of pitchers and managers wasting our damn time.
Granted, some attention-craving loonies do a much better job at putting on a show than others. Some are clearly in good physical condition and go all out with with a costume, or completely naked, and manage to evade security for awhile. While others are just drunk fat dudes who make it about 10 feet beyond the bleachers.
Not that it matters, because it's always a good time. And the best part of the experience for the rest of us fans is seeing the demented nut bag get leveled by an excessive number of security guards.
Here are the best 25 fan takedowns in sports.