It's unfortunate that Sprite itself didn't really get absorbed into much of anything, and so doesn't have much of a footprint and isn't really remembered outside of LFS and a few even more niche bits.

But I think the Sprite kernel and the Sprite-specific libraries (Pfs, Pdev, Fs_Select, Td_), as well as the Sprite-specific userspace, were pretty incredibly pieces of software given the limited resources they were created with.

For that matter, John Ousterhout's text editor and terminal emulator, mx and tx, were the substratum that Tcl was built on. There's a single library on Sprite, libmx, which mx and tx are based on. Tcl basically grew as the command language of libmx, originally two separate entities, then by mx 2.4 it was fully incorporated:

  eery@cherimoya [1] > cd /sprite/src/lib/mx
  eery@cherimoya [4] > grep Tcl *.c
  mxCmdAM.c:    Tcl_Interp *interp;
  mxCmdAM.c: Tcl_Return(interp, Cmd_BindingGet(mxwPtr->cmdTable, argv[1]),
  mxCmdAM.c: interp->result = Tcl_Merge(bindingCount, bindings);
  mxCmdAM.c:    Tcl_Interp *interp;
  [...]
  eery@cherimoya [10] > grep LIBS ../../cmds/mx/local.mk
  LIBS  = -lc -lmx -lsx -lcmd -ltcl -lX11

  eery@cherimoya [11] > ls /sprite/lib/sun4.md | grep tcl
  libtcl.a
  libtcl5.a
  libtcl6.2.a
  libtcl6.3.a