There is a watermelon at the center of all my effects...

Details
-This is a saved game
-New effects that I place do not have this problem
-Attempting to make them invisible using the Color tool did not work

I believe the effects use that model, which is usually made invisible.
I’ve seen the same problem with Adv Duplicator (Although Adv Duplicator is recommended over save games), so I don’t think it’s fixable.
You will probably have to make new effects each time you load it.

(In case you want it: Adv Duplicator can be downloaded using SVN. It’s included in the Wiremod SVN. SVN Tutorial: http://www.facepunch.com/showthread.php?t=688324 )

try getting a weapon other than the physgun out. ie; choose the gravity gun. that should make the effect symbols malong with the melons go away.

Savegames are bugged beyond reason anyway

adv dupe does the same thing. effects are only good until u quit.