Gears of War

This achievement speaks for itself - simply kill one hundred enemies with the Chainsaw function of the Lancer in ranked matches.

As every player is equipped with a Lancer at the start of each round, this can be done on any map. To get a chainsaw kill, approach an enemy (standing or downed), and hit "B" to rev up the chainsaw blade. If you successfully lock on to the enemy, you will perform a vicious slice through the enemy's torso.

However, be careful when performing this kill, becuase if you get shot whilst revving the chainsaw, you will be momentarily stunned, preventing you from moving and thus making you very vunerable to the enemy.

If you are suicide boosting for the Seriously achievement you can save yourself a weapon boosting session with this method. Please look at the details of suicide boosting in the achievement guides for Seriously. This is not a forum on what method is best for boosting Seriously. If you prefer suicide boosting this method will help you.

Make sure you are suicide boosting on the War Machine map.

Before the session starts, ask to be one of the people who gets grenade tagged. After you are tagged, use your chainsaw.

Keep in mind that if you are the last 2 people alive when tagged, using the chainsaw typically guarantees that you will win the round. Adjust accordingly.

If it doesn't unlock after exactly 100 kills, so what? you've got 10,000+ chances to get it right.

This method will save you a weapons boosting session and anyone who has boosted Seriously knows that every hour counts!

This isn't really a solution, more some advice for people trying to unlock the various kill related achievements as quickly as possible - at the end of every boosting session you should play a quick one round local match against a second controller before quitting to dashboard or turning off your xbox. I've done this and unlocked Seriously yesterday pretty much bang on 10000 kills. I've also unlocked all the weapon kill achievements after 100 kills.

I think what's going on is that sometimes, for whatever reason, the progress you make in the last match of a session isn't added to the various achievement counters. I first noticed this when boosting the 'Win 20 matches on map X' achievements - if I won 20 matches in one session the achievement would pop, but if I spread them out across multiple sessions I'd have to play 21, 22, sometimes 23 matches depending on how many sessions it took.

Of course, it's possible I've just been really, really lucky - there's no way I can prove this works. If people start trying this and it doesn't work out let me know and I'll take this solution down.