For exploration purposes a list of only the largest and smallest or otherwise special planets. This is by no means complete list, it would be pointless, this is more like a TOP-10 or even a top-3 would be enough.
List is collected and verified by CMDR Snake Man, the other sources list is something I cannot confirm, yet.
Smallest:
170km, Pleione 3 A
190km, Nu Tauri 1 A
374km, Kuk B 1
384km, Shakal A 1
412km, Oresqu A 1 A
421km, Q Centauri 4 A
441km, 9 Puppis
447km, Hip 71018 A 3 C
449km, Shakal B 3
461km, Maca A 2
473km, Wregoe Jt-z D13-92 4 A
These smallest planet(oids) are more or less going to have at least some potato shape on them, at least some of them. However planet to be small does not necessarily mean its potato shape, few of those really small planetoids are spheres.
Largest:
12,930km, Wolf 562 1
15,763km, Achenar 3
Usually the larger the planet, the larger the gravity. You should not land on planets with much larger than 4g gravity.
Other sources:
HIP 102918 1 A
smithys claim in dahan, smallest high metal content
COL 173 SECTOR CI-G C12-4 2 A, smallest rocky
PW2010 258 3, largest rocky
S171 20 7 a a
S171 19 A 6 b a
Ammonia worlds:
Largest:
7,100km, Snake Sector MS-T C3-10 4
11,010km, Snake Sector CL-Y D67 A 3
15,233km, Snake Sector FW-W D1-88 11
15,915km, Snake Sector Fw-w D1-36 A 5, with rings
18,782km, Eembaitl YJ-R d4-19 10
Earth like worlds:
Largest:
6,185km, Crookaae Zp-m D8-22 C 5
6,682km, Snake Sector Sj-q B5-4 6
6,929km, Plaa Aescs Di-i D10-30 3
7,209km, Byaa Aerb Ze-r E4-12 Ab
7,337km, Blu Aescs Oy-y D1-42 6
7,686km, Froals Ru-m D8-31 Ab 3
Water worlds:
Largest:
10,336km, Puekoa Sk-c D14-61 A 2
10,371km, Blo Airm Af-r E4-616 1
10,612km, Blo Airm Xd-k D8-126 Abc
10,643km, Plaa Aescs Di-i D10-30 4
12,102km, Byaa Aerb Lg-n C20-16 3
12,254km, Snake Sector Kr-w C1-17 2, with rings
12,383km, Snake Sector Fh-l B8-1 A
12,406km, Snake Sector Uj-q B5-6 Ab 2
12,676km, Snake Sector MS-T C3-2 B 1
12,896km, Snake Sector Ir-w D1-101 2
15,709km, Snake Sector El-y D108 5, with rings
16,022km, Snake Sector Fw-w D1-96 Ab 8, with rings
17,091km, Snake Sector GW-W C1-1 AB 2, with metallic rings
17,944km, Smojue Kd-a D14-12 1