Gears of War 3

As the above have suggested not a hard achievement with the fact of being able to start from any wave you died on.

To make these even easier here is what i suggest:

Make the game in private and invite your friends/recent gamers to join and you get to choose the map as well as adjust the difficulty down to casual.

If at any time you get bored or frustrated with the game simply leave horde mode and you can return in private game to the wave you was on last IE if at wave 6 you have to turn off and go when you start up next go to Private match - wave start and choose wave 6. Also if you forget which wave you was on browse to the stats menu at the main menu and RB until you reach the achievements and browse to this one and in the information it will tell you which waves you have completed.

try to always save money on the final wave to "buy back in" if you die if i remember off the top of my head it is 1200points to do so.

If you die then just continue as any money you raise in that wave will still be there on the next continue! you can store money up and up then when you are ready build defenses and ammo up and destory the grubs!

Hope this helped please vote positive if so :)

(sorry for any spelling errors)

This achivements is quite easy, but there are some things you have to keep in mind. to get this achievement you need to play the first 10 waves and you have to be in there from the start. Also every 10 waves is a boss wave which can vary between a reaver and the fearsome lambant beserker (there are of course al lot more boss types)
To make this achievement even easier set the difficulty on casual and put the following mutators on.
Instagib melee: you kill every enemy with a single melee hit (except for bosses).
Infinite ammo: well pretty much what it says (sadly only works on these weapons: lancer, retro lancer, hammerburst, gnasher, sawed off, all the pistols and the cleaver).
Super reload: when you make an active reload you get a 2x ammo clip (this doesnt disappear after a while) + massive damage bonus (you can kill a reaver with less then half a clip on insane).
Now just have some fun in horde and exterminate some locust.
Good luck

Edit: since people wanted to know how to unlock these mutators ill add them.
Instagib melee: kill 200 humans in beast with a wretch, to get this the fastest your best bet will be to play casual solo to get the most kills.
Super reload: get the bronze master at arms medal (100 kills with each starter weapon), easiest to make a private match against bots on casual.
Infinite ammo: get 100 combat engineer ribbons (get 5 repairs in 1 deploy), see vid