Are you looking for something light weight but still has the most important features you get from a full-blown Emacsen in your system? Then you can try some clones of MicroEmacs or uEmacs which will usually work for most editing needs. No dependencies and works out of the box even in small projects and suitable for things like Raspberry Pi or other such stuff.

For Ubuntu you may want to go here to find a debian packaged ready to use package or the full source as needed: