(BLUE SHIELD) - "Team Defense" - When in presence of allies, gain additional health boost and slight increase in speed (does not stack)
(GREEN CIRCLE) - "Runner" - Higher movement speed, additional jump height, harder to hit.
(RED TRIANGLE) - "Bullseye" - Lower recoil and sway on Sniper rifles, increased range, easier to spot enemies.
(ORANGE DIAMOND) - "Leader" - Increased stats while teammates are nearby, faster interaction as well.
(PINK DIAMOND) - "Guardian angel" - Save an injured teammate (or yourself) if shot down.
(BLUE CIRCLE) - "Gadgeteer" - Hack enemy tech from distance and through walls, cannot be spotted by enemy turrets or heatseekers.
(ORANGE PENTAGON) - "Basher" - Higher melee damage, increased stun chance and duration.
(ORANGE SHIELD) - "Stone wall" - Increased damage resistance (explosives included), slower movement speed.

"Clean" version available by this link - http://triplea096.deviantart.com/art/Titans-Defense-618486368

Just playing around with effects, trying to come up with random ideas