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It depends on what you want to look at with your 10" dob.
If you can access dark skies and like galaxies and other faint stuff - the eyepiece to get is an ultrawide angle (82 degree) eyepiece that delivers a 2mm exit pupil - just multiply the telescope's focal ratio by 2, to get the eyepiece focal length.
If you live somewhere bright and want to look at bigger brighter deep sky objects, then get an ultrawide angle eyepiece delivering 4mm or 5mm exit pupil.
You could compromise and get an eyepiece in between, with a 3mm exit pupil, but apart from use on very faint open clusters, I've never found much use for it in a dob, and think you'd be viewing sub-optimally on nearly everything.
One eyepiece is never going to be ideal for all types of objects one may wish to observe, unless there exists somewhere a very expensive zoom eyepiece that doesn't have a narrow field of view at low power (in which case, that's the one to get).
Cheers,
Renato
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