Well, I'm quite happy with T, which comes in both DOS and OS/2
flavors, it quite easy to configure and at about 9K can be stuck just
about anywhere, that emergency boot disk etc.
Available as ftp://ftp.pc.ibm.com/pub/pccbbs/os2_ews/tinyed.zip
Its free and quite useful for basic text mangling.
Another alternative would be pico from the dos pine distribution but I
refuse to use an editor that is bigger that the longest post I'll ever
make.
However, keep in mind that to many they are as protective about their
chosen editor as they are their daughter's virtue.