I have some boys who are pronouncing /th/ as /f/ at the ends of words: “bofe” for both, “wiff” for with, and so on. I went to www.onelook.com to get all common words ending in th (just put *th in the search box). Here is the list I’ll be using, and reinforcing:

1. with

2. path

3. bath

4. both

5. cloth

6. tenth

7. teeth

8. tooth

9. booth

10. fifth

11. sixth

12. tenth

13. math

14. moth

15. north

16. youth