1. Badminton Central Discussion F
This is a discussion forum dedicated to badminton.
http://www.badmintoncentral.com/forums/forum.php  

2. Archery Talk Forum
A forum community dedicated to bow and crossbow owners and archery enthusiasts. Come join the discussion about optics, hunting, performance, troubleshooting, styles, reviews, accessories,...
http://www.archerytalk.com/vb/index.php  

3. RealGM
Just missed the top 10.
https://forums.realgm.com/boards/index.php  

4. WhiteBlaze
WhiteBlaze is an Appalachian Trail discussion forum and information site, it also contains an exclusive photo section of Appalachian Trail photos. Hiking the Appalachian Trail One Blaze at a Time....
http://www.whiteblaze.net/forum/forum.php  

5. FFToday Forums
Forum has 2,897,138 posts.
https://www.fftodayforums.com/forum/  

6. KFFL Community
KFFL.com's sports discussion forums allow fans to interact and talk about current hot topics around the NFL, MLB and more
http://forums.kffl.com/forum.php  

7. The Lacrosse Forums
The Lacrosse Forums, an online discussion forum for men’s and women’s college, NLL, MLL, IWLCA, high school teams. Exchange ideas and playing tips, instruction, lacrosse equipment...
http://forums.insidelacrosse.com/forum.php  

8. TexAgs
Discuss all things Texas A&M and Aggies sports on the TexAgs forums and message boards.
https://texags.com/forums/  

9. UK Skateboarding Forum
A forum for skateboarders in the UK to talk about videos, spots, companies, riders and news. A bit like the Slap forums, but nicer.
https://ukskateforum.co.uk/