Formal:
* Respectfully yours
* With kind regards
* Yours truly
* Yours faithfully
* Very truly yours
* Best regards
Informal:
* Best
* Warm regards
* All the best
* Cheers
* Take care
* Regards
Creative:
* With heartfelt wishes
* Wishing you well
* With love and gratitude
* In gratitude
* Thinking of you
Specific:
* Thank you for your time
* I look forward to hearing from you
* Looking forward to our next conversation
* I hope this is helpful
The best option depends on the context of your letter or email.