Here are my picks for the top five most iconic covers featuring Adam Strange (with iconic being determined by what covers are most established and most recognized when it comes to Adam Strange, with a preference towards covers that are homaged a lot). This is not a BEST cover list and due to the very nature of icons, very few (if any) recent covers will be on the list. A notable exception to the rules is that I don't count covers from a character's first appearance (which isn't applicable to all characters, of course, just those who appeared on the cover of the comic they debuted in), as those tend to be automatically iconic so they're boring. Here's a list of all characters featured so far.
First off, while I'm exempting first appearance covers from the countdown, it's only fair, I suppose, to share them here before the countdown begins, so here is the first cover appearance of Adam Strange from his debut story, Showcase #17...
Artist: Gil Kane
Now on to the list!
5. Artists: Carmine Infantino and Murphy Anderson
Infantino usually did a great job boiling down exactly why Adam Strange was so unique as a hero. Also, you gotta give it up for any comic cover with two planets on it - kids love covers with more than one planet on them!
4. Artist: Ernie Chan
For a minor character like Adam Strange (albeit an awesome character), appearing in the Justice League of America comic was a big deal, as was this cover, which featured Adam's wedding!
3. Artists: Gil Kane and Bernard Sachs
Gil Kane's cover here captures the mood of an Adam Strange comic pretty beautifully here - action, science-fiction, crazy villains - it's no wonder that this cover was the one chosen for the Adam Strange Showcase Presents edition!
2. Artist: Neal Adams
Getting a Neal Adams cover drawing of you is a boon to pretty much any character, when it's as dynamic and memorable as this one, you're doubly lucky.
1. Artists: Carmine Infantino and Murphy Anderson
Once again, Infantino boils the essence of Adam Strange down into one striking cover - this one was homaged as part of the tribute to Julie Schwartz awhile back.