TA Game Commands (v3.1)
There are heaps of 'TA Command' lists on the net, but most of them include bogus or removed commands. The following list incorporates only those commands which I have actually got to work :)

General Commands
+clock
Permanently toggles the game clock on or off.
+switchalt
Permanently toggles ALT+# squad selection to #, and # of build menu page to ALT+#
+shootall
Instructs units to target everything of the enemies - not just hostile units
+noshake
Stops screen shaking due to explosions and earthquakes.
+bps
Displays recieve/transmit network stats. If recieve dips to 0, it is wise to reduce gamespeed to prevent your opponent dropping from the game
+sfx
Reduces level of special effects on the screen. Nanolathes and smoke is removed - reduces cpu lag
+dither
Permanently toggles fog of war dithered rather than grey. Very helpful on Ice and Metal worlds
+logo # #*
Change player colours in-game. # = 0-9 representing the colour of choice (Order is: Blue, Red, White, Green, Dark Blue, Purple, Yellow, Black, Light Blue, Tan). #* = player number (0 being yourself, with 1,2,3... being the other players in order of your F4 or spacebar player listings) - Settings do not affect what the other player sees
+contour #
Overlays a 3D contour map, # = 1-15. (+contour to turn off)
+showranges
Shows ranges like weapon range, sight and build distance
+makeposter
Creates large bitmap of battleground, saving to a sub-sub-folder in totala. (Disabled in multiplayer :P)
+bigbrother
Toggles through your units in order of build (repeat to turn off)
+sing
Normal unit sounds replaced by 'singing' (Horrible... just horrible :P)

Allied Commands (You must be allied with someone to use)
+shareradar
Instructs units to target everything of the enemies - not just hostile units
+sharemetal
Shares all metal with your allies
+shareenergy
Shares all energy with your allies
+sharemapping
Shares map information with your allies in non-mapped games
+setsharemetal #
Shares metal while keeping # amount for yourself. Type +sharemetal afterwards to begin sharing metal
+setshareenergy #
Shares energy while keeping # amount for yourself. Type +shareenergy afterwards to begin sharing energy

Game commands useful for watching recorded battles.
+view #
Can see AI's metal, energy and units. Use parameters View 1 for AI 1 etc (Player 1 = 0, +view to return)
+los
Toggles 'Permanent' LOS on/off (After +view #, typing +los will show you what player saw)
+lostype
Toggles between 'True' and 'Circular' LOS (Adjust for game specifics)

Change Game Options In-game (F2 | Options for GUI)
+gamma #
Changes screen gamma. # = 0-20
+shadow
Toggles all shadows including those from buildings
+fshadow
Toggles shadowing on features
+tshadow
Toggles shadowing on mobile units
+antialias
Toggles antialiasing on 3d models
+shading
Toggles shading on 3d models