*BEFORE READING, USE THIS COMMAND: /gamerule commandBlockOutput false*

        Okay, so you've probably seen my blog/tutorial on how to make items and tools sit on blocks (at least I hope you have, because your gonna need it). So this tutorial uses the same concept... Armor Stands. What will happen is that an armor stand will be riding an invisible baby zombie, and there will be players running around, and the zombie has an attack damage of 0, so you won't take damage, but you'll hear the "hit" sound effect, so you know if there's a powerup near you. As you know, zombies are attracted to players, so the zombies run up to the player(s), and you can kill your zombie (WITH COOL PARTICLE EFFECTS!!!). So to make a powerup that just "floats" around the world, you'll  need to use this command to spawn in the armor stand riding a baby zombie:
  /summon ArmorStand ~ ~1 ~ {Invisible:1,Pose:{RightArm:[-100F,-90F,0F]},Equipment:[{id:potion,Damage:8193,Count:2}],ShowArms:1,Riding:{id:Zombie,Silent:1,IsBaby:1,CustomName:Powerup,Equipment:[{},{},{},{},{id:emerald_block}],Attributes:[{Name:generic.maxHealth,Base:1},{Name:generic.movementSpeed,Base:.1},{Name:generic.attackDamage,Base:0},{Name:generic.followRange,Base:10}],HealF:1,ActiveEffects:[{Id:14,Amplifier:5,Duration:20000000,ShowParticles:0b}]}}
        Now some of this might confuse you, so let me clear it up. You summon an armor stand, that is Invisible, an then it has to have Equipment to hold the potion/powerup/upgrade. Then it MUST be Riding a baby zombie, an the rest of this should be easy to understand, so I'll let you learn (NO MORE TYPING FOR ME!!!!!). Oh, and the "F" stands for "Float", which is a Java keyword for a floating number (Java is the code that minecraft is made up of). This next part is optional. COOL PARTICLE EFFECTS!!!!! (RAINBOWS!!!!). So you will need a redstone clock (Not the item), a chosen particle effect (YOU ARE THE CHOSEN ONE, HARRY POTTER), and the command, as always listed:
/execute @e[name=Powerup] ~ ~ ~ particle spell ~ ~ ~ 0 0 0 10 100
        Once you kill the zombie, the powerup will drop. I do apologize for any missing characters because my keyboard is really bad, so add in any extra commas, spaces, or whatever needs to be added.
Thanks for reading!
    --TheTypingLizard