(Early modern = anything from pre-Civil War Tudor or Stuart England. Or the roughly equivalent time period in other countries, for that matter.)
Alas, my life list is not very long:
Edward II
Tamburlaine the Great (both parts condensed into one)
The Duchess of Malfi
The Spanish Tragedy (in a not-very-good undergraduate production)
The Revenger’s Tragedy (ditto)
The Knight of the Burning Pestle
The Witch of Edmonton
If filmed stage productions count, I’ve also seen Volpone and Dr. Faustus.
The Second Shepherd’s Play. Or is that too old?
The Changeling, by Middleton and Rowley.
Borderline-too-old, but I’ll count it anyway, since I’ve seen it too 
Gammer Gurton’s Needle
'Tis Pity She’s a Whore
(John Ford)
I don’t remember ever having the opportunity to see any of these, but for those of you who have, I’m curious how you’d rate them: “well worth seeing (in a decent production)” or “best left in the past”?
Jew of Malta
Dr. Faustus
Edward II
The local “Summer Players in the Park” alternate Shakespeare and Marlowe as their Classical playwrights.
Of the ones that I’ve seen, I’d say the standouts are The Duchess of Malfi (right up there with Shakespeare’s best tragedies) and The Knight of the Burning Pestle (grocer and his wife go to the theater and order the actors to perform something more to their tastes; very, very funny). But really, they’re all good fun – these are the blockbuster films of the era, and the playwrights knew how to entertain.
This would be 16th and 17th centuries, right?
A couple of Lopes (although I can’t remember any more which ones I’ve read, which ones I’ve seen live and which ones on TV; I like Lope’s works), La Celestina (which got me completely lost by the second paragraph) and La vida es sueño (which I didn’t like).
Also, when I was in High School it was customary for the 12th graders to organize a play with no teacher intervention: often it was a series of sketches, with each sketch offered by students from a different class and section. When I was in 10th, the subject was “short comedies or standup” and all of the 12th grader’s sketches were adaptations of Cervantes short stories (there was very little to adapt, they didn’t bother rewrite the stories as plays but simply play them out). Several of the other courses had recitations of comic poems from Quevedo or fragments from Lope.
I haven’t seen anything British from that period live - and given the language difficulties I know I’d have, I’ll probably refrain.
Jonson’s The Alchemist, which was hilarious.
I’ve probably seen others, but I can old recall reading them for certain.
Volpone
Edward II
The Rivals (Sheridan) – very amusing, it’s not staid and talky at all, it’s quite rowdy actually. Mrs. Malaprop, a character in the the play, is from whence malapropism: humorously using the wrong, but similar sounding, word (ie, “penis ensues”).
*Edward II *(the production tried to make him a Christ figure(!))
*Fuente Ovejuna *(translated into English)