battlefield-3
On the minimap I occasionally see small blue squares with little lines coming out of the corners. What do they mean? My first guess was that they were nearby explosions, but I think I see them too often for that to be the case.
EDIT: Here's a pic, you can see two in the lower left (they might be circles and not squares like I first thought).
The bar represents your progress towards the next unlock in that weapon group. The more you use a certain weapon class, vehicle, etc, the more you points you will earn toward an additional unlock in that category. You can see a more detailed view of this progression in your battlelog profile:
If it is a star, then it means that they are the squad leader. If it is an ammo clip or something like that, then that means that this person has a squad perk equipped. 
So, in order on the above picture, we have:
Best Answer
Blue
ยคon mini-map means friendly anti-tank mine or friendly C4. You can also see these symbols over them when you're nearby. Even in HC mode.