12'' disc sander is my tool of choice. i have a powermatic 6''x48'' belt with 12'' disc. You would not believe how much you use it when you have it. Great of truing up pipe ends.
End grinder and flapper wheels for sure. Another one of those where you wonder how you did without one.
There's a lot of tools that are available for every little thing. That's where
you need to decide between wants and needs. With tools, you can never have enough ! It's like welding machines, one is not enough !