I need to know the correct grammer for invitations.  Which verbage is
correct>  Unlimited Holdings (our company) requests or request the
pleasure of your company for their annual Christmas Party. And the
other invitation is "Brittany and David (my husband and I) request or
requests the pleasure of your company for their annual Christmas
party.

The following are correct:

Unlimited Holdings requests the pleasure of your company for its
annual Christmas party.

Brittany and David request the pleasure of your company for their
annual Christmas party.

The key here is proper subject-verb agreement. In the first example,
"Unlimited Holdings" is a single entity, so it takes a singular verb. 
(I also changed "their annual Christmas party" to "its annual
Christmas party" for the same reason.)

You may find the following grammar guide useful in this regard:

Grammar and Style Tips
http://www.aom.pace.edu/ame/Guide%20lines/style_tip.htm

Do a search on that page for the word "company" to see an explanation
of how company names are singular.

The second one is a bit trickier.  "Brittany and David" could be seen
as a single unit, I suppose, but then you'd probably word it as "the
marital unit of Brittany and David" or something along that line (I'm
being a bit facetious).  Seriously, though, two people are doing the
inviting, so the plural verb can and should be used.

I hope this helps.  This answer is based primarily on my experience as
a longtime copyeditor (or copy editor, depending on which reference
source you use).

You also may find the following resource useful:

Subject and Verb Agreement (American Heritage Dictionary)
http://www.bartleby.com/64/C001/060.html

Best wishes,

mvguy-ga



Google search term: subject verb agreement grammar
://www.google.com/search?q=subject+verb+agreement+grammar&sourceid=opera&num=25&ie=utf-8&oe=utf-8

Please note, the correct spelling is "grammar" and not "grammer".