Want to be mentally tormented?

Around here, I guess its the "in" thing to do! Daniel has been telling us puzzles...like, well, this one was from Papa, but...

OTTFFSSE...
What is the next letter in the sequence?
Hint: Its not E
It goes on infinitely...

So, Can anyone figure it out? THere are alot of them around here...not all of which I have figured out...But, some are rather hard to tell on a blog. :) Let me know how much you are tormented...or if you get it...