Okay, I'm on the last tape to transfer to DVD, so time to check and see what eps I'm missing. Keeping in mind that Volume XIX is currently in the mail to me, and XX has been announced, there's a few eps not listed here that I don't have at the moment but will have sooner or later.

KTMA: I only have K05 and K13.
Season 1: 108-110 I have without host segments, I'm entirely missing 112 and 113. (Update: 111 has the middle host segments, but not the opening or closing.)
Season 2: missing 203, 205, 209 (pro version does exist, but is out of print...a used copy runs about $25 on Amazon, new copies $90+). (Update: 201 is trimmed like 111.)
Season 3: missing 302, 306-310, 313, 315-317, 321 (still in print, but comes with yet another copy of Manos).
Season 4: missing 411, 412, 416, 418.

I have everything from Seasons 5-10 in either pro or off-VHS form. So, leaving aside KTMA eps and the two that I could theoretically buy but might be a bit more expensive than I'd like, I'm missing 18 eps and have three more that I have poor copies of. Season 3 is my biggest hole, more than half the eps I lack are from that season. And a lot are never getting pro releases due to rights issues.