Is it ethical to cherry-pick reviewers based on their previous reviews of your manuscript? The academic review process is usually supposed to be blind, in that authors are not told the identity of the reviewers. But frequently it is possible to guess who has reviewed your work, or the reviewers themselves may let you know informally.

Say my manuscript is rejected from journal A after one very positive and one more critical review, and I think I know who the reviewers were. After some revisions I submit to journal B, who ask me for a suggested list of reviewers. Is it ethical to list the reviewer whom I suspect gave the positive review the first time, but replace the one I suspect has a negative opinion of my work with another reviewer? What if the positive reviewer is someone whom I did not originally suggest to journal A - is it ethical to suggest him/her to journal B in the light of their previous review?
There are ZERO ethics involved.  First, you suspect, but do not know, who the original reviewers were.  You may be right, you may be wrong.

Next, suggestions for potential reviewers are just that -- suggestions.  It is the responsibility of the editor to pick appropriate reviewers, and your suggestions are just one potential source of information in the process of doing so.

I'd say even if you recommend people who you respect to referee your papers, they'll surprise you regularly with critical reviews (if they're doing their job).

The biggest ethical quandry you can get into in the process of recommending referees is probably some sort of pre-arrangement with those you suggest.  This is to be avoided as less than stellar behavior.