Halo 3

Double EXP weekends and Griffball are both history in Halo 3 so I think your best bet is to head into Social Skirmish unless you're really, really good at playing Halo 3, and in that case, you probably already have this achievement.

The good thing about Social Skirmish is that it's a team list, so if your team wins, the whole team gets 1exp. Basically, you have a 50-50 shot at getting 1exp instead of something like Rumble Pit where only the top performers get something.

A few marathon sessions and you should be able to gather 50 exp (50 wins). Tedious, but if you want the achievement, you need the 50 exp. Boosting works as well if you have lots of friends.

To get this you must reach the rank of Lieutenant in any one playlist on the new EXP system.

If you haven't already gotten the Spartan Officer achievement then it will unlock at the same time as unlocking this achievement too and not by obtaining a global officer rank like the previous requirements state.

The way I did it was to take advantage of a DoubleEXP event such as Grifball or Rocket Race. Doing so will award you a lot more than the other playlists and in theory, you will only need to win 25 matches in order to reach this rank - I did it from 0EXP in one day on Rocket Race with a friend.

To earn Lightswitch (and Spartan Officer from the retail disc at the same time) you must earn 50 EXP in a single playlist. You can check this by selecting your gamertag in a lobby and looking at your stats, and the area at the bottom right will tell you how many EXP you have in that playlist. Your "Total EXP" does not matter, what you are interested in for this achievement is to the left of that stating e.g. "Rumble Pit EXP".

To do this solo, I would recommend team playlists and praying that your teammates aren't playing on donated consoles at the local mental ward. Each team win is 1 EXP closer to the achievement, though each team loss is simply lost time because you get no experience for it. Free for all modes may be your thing if you can consistently score well (not necessarily first place) because the top four spots all receive 1 EXP in Rumble Pit.

However, if you're interested in a more time efficient method and don't mind a bit of boosting, you can party up in social and play rumble pit. You want to veto anything that is not slayer or swords because every other game type makes it difficult or impossible to distribute the experience points. If you end up stuck with a gametype that you can't balance, just pick one person to own everybody and end the match as fast as possible. Take note, however, that all five DLC packs or the ODST bonus disc are required to play rumble pit.

Assuming everyone cooperates over the length of the session, you can finish this achievement from 0 EXP points in 3 hours for all 8 people involved. In rumble pit, the top 4 all receive one experience point at the end of the match. This is most easily accomplished by everyone getting one kill to tie for second, then having one person go nuts until they win the match. It is very important that everyone ties for second, because the leaderboard is still enumerated. To explain what this means, I will give a small example:
#1 gamertagA 20pts
#2 gamertagB 2
#2 gamertagC 2
#2 gamertagD 2
#2 gamertagE 2
#2 gamertagF 2
#2 gamertagG 2
#8 gamertagH 1
Notice how gamertagH is eighth and not third, which means he gets no EXP for that match.

Ideally you want no guest accounts and no zero scorers to stave off the ban hammer until after you're finished. I know enough of network programming and pattern recognition to tell you that it is not difficult at all for an automated system to tell if a guest account is simply *there* as opposed to someone actively playing it, and rubberbanding your controller does not fool anybody at Bungie. To get this done with maximum speed and efficiency, I highly recommend 8 actual people, and that each one of them remains to continue the method even after they are finished.

Why rumble pit? Free for all modes are the only way you can get everyone an experience point at the same time. Though it is likely that many people have a lot of existing experience in team modes like Team Mythic from attempting the achievement on their own, it makes a poor choice for boosting because the losing team from each match will get no experience. In addition, the teams will not always be distributed the same, and it is very likely that a few people could make out like bandits and a few others could get the shaft. It's extremely unpredictable and likely completely unfair.

To elaborate on Halo bans, all that happens when you are caught boosting is that you are banned from gaining experience for a short period, usually two weeks. You are not banned from XBox, banned from playing Halo online, nor are any of your EXP totals reset or adjusted in any way. As a matter of fact, you can continue to unlock multiplayer achievements, so you could, for example, participate in a session to unlock DLC achievements while EXP banned.

You need 50 EXP in one playlist for this and the quickest way to do it is to boost them.
You need one person as a quitter (must have 4 controllers and an useless account).
You can boost 4 accounts at the same time (they don't have to be on one console).

First you need to change your language for the quitter and the booster party leader, it works best with chinese (the very bottom one).
On the bottom you see a vid how to change a language, so you won't have any trouble changing it back to your language. (it's the old Dashboard in the vid, but works the same)

When you have your language ready,
Booster party leader: go to Halo 3 Matchmaking lobby, then invite your friends, who also wants to boost this, or turn on your guests. After you have 4 players in your lobby, go to Social Skirmish or Team Mythic playlist (Must have all DLC) then press "X" and select the bottom one from the list. The quitter has to do the same (turn on guests, go to the playlist, press "X" and make sure you have to bottom one always enabled).

If you have done everything correctly, it should always find your boosters and every time just quit with the quitter, so your boosters gain 1 EXP per match. You can boost as much as you want, (for example boost rank or playlist rank) without getting banned. You can also do some other Achievements while you're doing this, but I suggest to get EXPs first and then boost the other Achievements, because it can get you banned from earning EXP.

There is many different methods for this, but the fastest is:
1. chinese language
2. 2 consoles, 4 controllers on the quitter's console and 4 controllers on the booster's console.
3. 3 guests on both consoles.
4. Social Skirmish
5. quit fast and start the game fast.

You should get this done in 1 hour. Good luck and hope this helps. ;)