Halo 4

EASY MODE:
Start throwing sticky grenades about, if you get a kill from the grave with one, this achievement unlocks.
I have no idea why, but it has worked on 2 separate accounts.
Credit to Soaring Eagle5 for helping.

In an effort to consolidate the five guides all explaining the same thing but differently, I'm putting this guide up.

This achievement is bugged.

Not bugged as in if you do the things it asks for it won't unlock. Bugged as in the most random thing you do will get you the achievement. As proven by it's near 100% completion rate. This one unlocked for me on Harvest. I was Needlering two players, died, and killed one post mortem. Then it unlocked. Given the guides to this achievement. Looks like if you or your target are in the air when the kill is made, or you earn said kill post mortem, it unlocks.

The way you are supposed to earn this achievement is to be airborne from a ManCannon and kill another player. Wreckage has on ManCannon for each team and gives you nice air time. Though I would recommend softening up a target sitting where said ManCannon spits you out at before you go into it. Alternatively, ezmode way is to grab Rockets and blast someone sitting on the ridge while in midair from same ManCannon. Or wait near one and follow another player through it right after they do and assassinate them in midair.

It's also possible to achieve this on Shatter. On either base there are two Grav Lifts. These also count as "ManCannons." These are where I earned Clay Pidgeon and Special Delivery as well. Simply stick someone, dart into ManCannon and viola. Alternatively, if you drop into it from the upper level where the Grav Lift spits you out, you'll bounce up and down rather than get forced out. From there, earn a kill and again: Viola.

Harvest has Grav Lifts as well but they are buried behind where you initially spawn and on the ends of the greenhouses in the middle.

Just unlocked this one, and I did not do as the description says.

I was playing Extraction on Shatter. I went to convert a station, and unlocked it while inside the building. There was no Man Cannon around.

So, it may be a glitchy achievement, or perhaps I was lucky. Just thought I'd throw this out there for anyone else.

EDIT: Seems like nearly everyone else has encountered the same thing. Achievement unlocks, well, kind of whenever. Many have reported not fulfilling the condition and having it unlock for them. Also seems like it doesn't need to be in Crimson matchmaking either. People have reported unlocking this playing SWAT.

Here is a quick video on how to get it at the start of a match.

When you are in the blue team on Wreckage. Quickly Grab The Rockets and kill someone in mid-air with it. Very Simple.

it must be glitched as i had my warthog boarded and i got a nade kill on the hog straight after and it unlocked i did not even jump so unless me coming out of the hog counted as being mid air i dont know

anyway my friend got this properly all he did was get a rocket launcher and waited for someone to be in a man canon path then picked up an easy rocket kill while in the air. maybe use camo and dont attract attention by shooting people stay hiddin and chose your moment carefully

I was able to get this Achievement on the Shatter map and I had jumped off of a building and got a kill (head shot) and it unlocked. I have 4 other people that I wa boosting with and we all received it the same way. Or the solution as described by the Achievement works just as well.

ODST - 30G (Requires Crimson DLC)

Difficulty: 2/10

This Achievement can easily be unlocked by either weakening an enemy or boosting partner and then escaping into a Man Cannon and finishing them while in mid air.

You can also easily get this by sticking an enemy with a Plasma Grenade and jumping in a Man Cannon before the grenade goes off.

NOTE: This Achievement has been confirmed to be bugged and may actually unlock without you even trying for the Achievement.