This is a little patch I slapped together that changes the last 3 weapons.
Here they are:

Rocket Launcher -> Hand that throws M-100s
Plasma rifle    -> Bottle rocket launcher
BFG9000         -> A pipe that launches the firecracker of total oblivion

The tools I used to make this were:

WinTex 4.2
DeHackEd 3.0a
DeuSF
PC Paintbrush 1.0 by SoftKey Software 
and the text on the title screen was from ftp.cdrom.com. Look for
DOOMFONT.ZIP

Type INSTALL to load the patch.
Type RESTORE to unload the patch.

This patch by One Man Team Software. (Jeremy L Wagner)

E-Mail: lwagner@mwci.net
Web-Site: http://users.mwci.net/~lwagner/ironlich.htm