The Submissions Grinder has full payment details in now, as of a couple of weeks ago, so you can easily search & sort there.
Off the top of my head, though...Terraform
is a top payer, at 25c a word. 2000 word limit, near future SF only, and they don't respond in the case of rejection... but 25c a word, man. And by all accounts, if they do like your story, they are actually good to work with. It's just the rejections thing that bugs me.Fantastic Stories of the Imagination
is 15c a word for up to 3000 words, any speculative genre.Fireside
, when it's open (about one month per year), is 12.5c a word, and open to literally anything--not just spec fic, though it leans that way. I think its limit is 6k now.Clarkesworld
is 10c/word for the first 5k, 8c a word thereafter, and tough to get into.WotF
only actually pays standard pro-rates of 6c a word--the higher pay rate only kicks in because of the flat-rate prize money, which therefore depends on your placement and your word length. I did work out that I got 72c a word for Squalor & Sympathy Anyway
, when you actually do the sums, none of this actually makes that much difference in the end. It is literally quibbling over cents
so as nice as an extra $20 is, I tend to submit in order of prestige rather than pay. They tend to go hand in hand, to be sure, but in general I'll submit to F&SF first as the market I most want to break into, then Clarkesworld & Asimov's, and work down from there.