I have patched tim4i's old m1redux weapons plugin for the official Marathon. This plugin replaces the old weapon sprites with HD variants. Some textures have been refined even further from the original using GIMP to edit them. According to Tim4i, you should not unzip this file but I've found it works regardless. All credit goes to both tim4i & herecomethej2000s as this was their original work, I merely patched the file. The original licence restrictions still apply.
-You need OpenGL to run this pack.
-This plugin is for the official Marathon 1 (not M1A1).
-I did NOT get permission from tim4i to create this patch. He hasn't been online since 2012 and left no means of contact. No copyright infringement intended.
Post any glitches/problems you find here: http://pfhorums.com/viewtopic.php?f=13&t=39240
-Fixed a transparency/eraser mistake I made with the pistol that I didn't fully fix in the last revision.
-Rounded the tip of the assault rifle to make the barrel appear more realistic.
-Antialiased the fusion gun ever further.