Just one more point, a canonical is just a hint to the search engines, it is not a directive, so if they think that the pages should not be merged, they will ignore them, so in that way, they may make the decision for you

no not like a noindex. more like a merge.

will it make you rank for many keywords? not necessarly, as a page all about blue widgets is going to rank higher then a page has many different subjects including blue widgets.

A canonical is really for duplicate content, or very alike content.

So you have to decide what your page is, is it duplicate or alike content, or is it unique?

if the pages are unique then do nothing, let them rank. if yopu think they are alike, then use a canonical. if there are only a few, then i would not worry either way.

if you decide they are unique, they I would look at making the page title unique also, maybe even description too.