Also a person who ousts someone.
jouster
juster
muster
Yes, in that you can add -er to (almost?) any verb to make an agent noun, but I think that even you would be hard-pressed to find it used like that in the wild amongst all the legal usages.
A tool, often improvised from a piece of old cloth, to remove dust.
daster
A loose Filipino dress.
Zaster (colloquial German: money)
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Easter 
easer
As this Oil is very anodyne, or an Easer of Pain, it is excellent, taken inwardly, to cure Hoarseness, and to blunt the Sharpness of the Salts that irritate the Lungs. In using, it must be melted and mix’d with a sufficient Quantity of Sugar-Candy, and made into Lozenges, which must be held in the Mouth as long as may be, before they melt quite away, swallowing it down gently.
– The Natural History of Chocolate, 1730
eraser
e-laser
A device emitting a beam of coherent photons, controlled over the internet
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(if it doesn’t exist yet, it will.)
(Can’t find a citation, so either I’ve just invented it, or its not called that.)
Consider the foregoing:
erased
eased
I reply to your word with ease
easy
peasy 
(“lemon squeezy”)
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Peas
So close to peace, yet so far
Pease
The non-countable word which later came to be considered as ‘peas’, plural of ‘pea’ [Edit:this is wrong. See Wiktionary]