NetSurf is a multi-platform web browser for RISC OS, UNIX-like platforms (including Linux), Mac OS X, and more.
Amaya
Opera used Presto up to version 12.x. Later versions use Bink, a Google fork of WebKit.
Viola (no longer maintained)
Dillo
Links+
Avantbrowser
Maxthon (no longer uses (only) IE render engine).
Midori
Uzbl
xxxterm is a minimalists web browser. It strives to be vi-like for heavy keyboard users while maintaining traditional web browser behavior. It is ISC licensed.
xombrero the new renamed version of xxxterm.
Otter Browser
surf is a simple web browser based on WebKit/GTK+.