what size lures would you guys recommend using on a 6'6" rod medium action, spinning reel?

1/8-1/2 oz or so.  It will vary a lot from manufacture to manufacture.  And that doesn't mean that you will be able to set the hook with a 1/2 oz jig or spinnerbait, but you will be OK with a 1/2 oz rattle trap.

there should be a lure wt. suggestion on the rod... if not, I wouldn't throw anything more than 5/8.. BUUUUT I'm not 100% sure. I'm setting myself up for getting laughed at.

That's about right.  Look at what the rod says on it for recommended weights of lures.  Roughly, most rods fall in the 1/4 to 5/8 range, some will be as low as 1/8 and some will be as high as 3/4.  Depends on who made the rod.

there should be a lure wt. suggestion on the rod... if not, I wouldn't throw anything more than 5/8.. BUUUUT I'm not 100% sure. I'm setting myself up for getting laughed at.

That sounds about right. 1/4 to 5/8oz.

BB

In the normal order, lures for the target species are selected first,

then a rod is chosen to handle the lure selection.

Roger

I'm not a real scientific or technical fisherman so I just use what ever I want.  I'm usually not to far off the rod parameters but carrying only 1 rod I may put a 3/4 oz or 1 oz spoon on a rod designed for 5/8 and think nothing of it.  I can go the other way, will put a fly on spinning rod and just work the trough 10-15'.