RWS Co2 wadcutters have always worked well in my 586 revolver. They are a consistent fit and need a definite push to seat them flush in the magazine.
I've tried other types of quality pellets, both pointed and roundhead, but I found that they dropped into the magazines inconsistently and so I reverted back to the above mentioned wadcutters.
That's what I use in my 586 and CP99. fantastic budget pellets and work every time.
Geco in the Umarexes, although the S&W likes superdomes. FTTs work well in the P09 and feed without issue. They are pretty good for a relatively heavy pellet.