I enjoy and print all sorts of sizes 4"x5", 4"x6", 5"x7", 8"x10", 9.5"x12" (recently), 11"x14", 12"x16" and (rarely) 16"x20".
The image area on the print varies with the image and original film format.
My largest frequent print size is 11"x14", so much of my temporary darkroom setup is oriented toward that size.
The next size up is 24"x30" from then on you were into roll paper; this is (was) colour negative print paper.
My favourite sizes that I print are 5"x8" which is half of an 8"x10" piece of paper, but one that the 35mm frame works very well with, followed by A4 paper (Ilford) which is 297mmx210mm, this enlarges almost perfectly with 35mm framing as well.