Heads Up! is a secret Medal. It unlocks the Tin Man mod.
Walkthrough
This is the hardest medal to achieve. Future Soldier's head in a helmet is located in the top left corner of the Gorge map (the small version of Canyon). To unlock this medal, you need to reach it. However, you can't climb up there by jumping, so you need to blow yourself up.
To make the process easier, you can go to a custom battle on Gorge and activate the Sky9 Mod, which adds super physics to the battle. This way, it will be easier to fly above the head. If you go off-screen above or near the head, you can also get the medal.
Best weapons for blowing yourself are rocket launchers. You need to shoot below yourself. It is not recommended to use Dragon's Breath rocket launcher, because then you will Body Pop, and your body would be ripped apart instead of reaching the sky. Best rocket launcher for blowing yourself up and reaching the head is M202/Bennett's Doom, as they have a lot of impact and they do not use body pop. You can also let your enemy who uses a weapon with strong push force to kill you and push you up. Weapons with strong push force are shotguns R870 and DB12 (and their custom variants), and custom melee weapon Sky9 Iron (with the highest push force in the game).