According to PETA: http://www.goveg.com/f-top10ballparks_major.asp

1. Citizens Bank Park (Philadelphia Phillies)
2. AT&T Park (San Francisco Giants)
3. Safeco Field (Seattle Mariners)
4. PETCO Park (San Diego Padres)
5. Busch Stadium (St. Louis Cardinals)
6. Coors Field (Colorado Rockies)
7. Rogers Centre (Toronto Blue Jays)
8. Dolphin Stadium (Florida Marlins)
9. McAfee Coliseum (Oakland Athletics)
10. (tie) Minute Maid Park (Houston Astros)
11. (tie) Chase Field (Arizona Diamondbacks)