I thought a few of the other days so far this week had easy challenges, but today is super easy.  If you still need the weekly challenge, today is likely the low hanging fruit of the week.
 
750cR - More than a Handful
      Kill 77 enemies in multiplayer Matchmaking.
Just play 4+ matches, depending on how many kills you can average per match.  I suppose if you play objective or dominate in multiteam you could get this done in fewer than 4.

2500cR - One Spartan Army
      Kill 250 enemies in Firefight Matchmaking.
Two or three matches of Gruntpocalypse in score attack will give you this.
 
2000cR - Hyper Lethal Vector
      Kill 100 enemies with headshots in Firefight Matchmaking.
You should manage 100 headshots during the 2-3 matches needed to rack up 250 kills for One Spartan Army.
 
600cR - Blast Radius
      Kill 30 enemies in Firefight Matchmaking with grenades.
Not sure if you'll get this or not during the One Spartan Army and Hyper Lethal Vector challenges.  I tend to hang near  an ammo dump and pick off grunts from a distance so I don't pick up many grenades.  But you should be able to manage a decent number of grenade deaths in the initial play throughs and then play a standard score attack or whatever and go aggro to pick up extra grenades + die a lot to get the two you spawn with.  Shouldn't take long.
 
And if you want to mix things up, you can obviously hop into some 4 player firefight matchmaking.  I have fun with that in 3 or 4 match doses.
 
5850cr for 4 fairly easy challenges.  Plus 2000cr for the weekly if you don't have it yet. 

I thought a few of the other days so far this week had easy challenges, but today is super easy.  If you still need the weekly challenge, today is likely the low hanging fruit of the week.
 
750cR - More than a Handful
      Kill 77 enemies in multiplayer Matchmaking.
Just play 4+ matches, depending on how many kills you can average per match.  I suppose if you play objective or dominate in multiteam you could get this done in fewer than 4.

2500cR - One Spartan Army
      Kill 250 enemies in Firefight Matchmaking.
Two or three matches of Gruntpocalypse in score attack will give you this.
 
2000cR - Hyper Lethal Vector
      Kill 100 enemies with headshots in Firefight Matchmaking.
You should manage 100 headshots during the 2-3 matches needed to rack up 250 kills for One Spartan Army.
 
600cR - Blast Radius
      Kill 30 enemies in Firefight Matchmaking with grenades.
Not sure if you'll get this or not during the One Spartan Army and Hyper Lethal Vector challenges.  I tend to hang near  an ammo dump and pick off grunts from a distance so I don't pick up many grenades.  But you should be able to manage a decent number of grenade deaths in the initial play throughs and then play a standard score attack or whatever and go aggro to pick up extra grenades + die a lot to get the two you spawn with.  Shouldn't take long.
 
And if you want to mix things up, you can obviously hop into some 4 player firefight matchmaking.  I have fun with that in 3 or 4 match doses.
 
5850cr for 4 fairly easy challenges.  Plus 2000cr for the weekly if you don't have it yet. 

Why can't these be on weekends? The amount of time I have on weekdays is enough for maybe 3-4 matches....

" Why can't these be on weekends? The amount of time I have on weekdays is enough for maybe 3-4 matches.... "

Yeah, I'd probably want an hour to knock these off.  It might go quicker, but if you have a few bad multiplayer matches it could take longer than planned for 77 kills.
 
20-30 minutes for the Gruntpocalypse, then however long it takes to get 77 kills.

I'm probably going to jump on today and see if I can pick up some of these challenges, although I still maintain my stance that I'm not going to farm gruntpocalypse just to credit boost.

Thanks for raising my awareness to this, means I got the weekly challenge. 
 
I did however put aside all my uni work to do it, so now feel bad.

you realize this post will be obsolete tomorrow right?

" you realize this post will be obsolete tomorrow right? "

" @blacklabeldomm said:

" you realize this post will be obsolete tomorrow right? "

Live in the now man. "

Meh.  Monday's Challenges were faster.  Had them all done in a couple hours if that.

Looks like I have some things to do tonight after Giant Bomb's TNT.

yeah these were pretty easy.

Yep, I think today is even easier if you are cool with using custom firefight to get 400 kills quickly.  
 
I picked up 6 assists and 5 CQC kills pretty easily in one multiteam match.

Just to add a little information to your comments for folks who may not know...
 
You can simulate an online firefight by choosing "Score Attack" from the game modes.  This allows you to solo maps and get credit towards challenges.
 
Both gruntpacolypse and Sniper Attack have 5 waves and 120 enemies total and while the type of enemy is never variable the composition of the enemy force does seem to have some random elements, especially with the brute wave.  Some games you'll see 2-3 gravity hammers and some games you won't see a single one..  Gruntpacolypse puts you against a pure grunt force and from what I can tell each wave adds more grunts carrying fuel rod guns and the plasma shooters.
 
Sniper Attack has 5 unique waves of enemies but they are always spawn in the same order regardless of which map you're on etc.  
1.  Grunts: Just standard grunts with a few specialists and heavy weapons mixed in. 
2. Vultures:  Several groups of 4 vultures spawn.  3 vultures will always have shields, one will have either a beam rifle or needle rifle.
3.  Brutes:  Mostly just brutes with spikers.  There are numerous chieftains as well and I've seen them carry either hammers or concussion rifles... sometimes they'll all have rifles and sometimes most will have hammers.
4.  Skirmishers.  This is by far the hardest wave.  Basically a bunch of vultures who don't have shields but carry much better weapons and have the ability to leap quite far.  Switching to the pistol for this wave is almost always the best idea because they are agile, travel in packs, and if you get bogged down reloading the sniper rifle you'll end up dead.  Perhaps the most dangerous part of this wave is their leaping ability.  If you do not keep your back to a wall odds are they'll probably find a way to your unguarded rear because they do not need to worry about using ramps to get you your level.
5.  Elites, Hunters, Grunts:  This wave doesn't spawn like the others, they come in on covenant drop ships so you need to watch out for their vehicle mounted concussion rifle (two sniper shots take this gun out though).  The only consistent thing in this wave is the number of hunters.  The drop ships will always drop off 2 hunters, never more and never less.  The drop ships can drop 4 or 8 elites.  If 8 you get fewer grunts in that wave and if 4 you get more grunts in the wave.  Your sniper rifle will kill hunters in 3 hits IF you manage to hit their flesh and see orange blood.  If you hit their armor (worn armor, not their shield) it seems to take between 6-8 sniper bullets to knock them down.
 
 
One Spartan Army will take 3 solo sniper attack or gruntpacolypse games assuming you are able to clear the enemies before the clock runs down. 
Hyper Lethal Vector can be done in a single gruntpacolypse as there will be 120 enemies in total.  Just focus on accuracy and it's cake.
Blast Radius is a bit of a pain to do but if you just want speed throw your grenades and die intentionally, throw more grenades, etc.

This is exactly the day this week I got the weekly :D Today's certainly harder...

" @Teran:  Wow, excellent stuff.  The only caveat I'd add is gruntpocalypse doesn't seem to have 120 enemies every single time.  I completed a round on this challenge day (forget which map) and I had 111 or 112 kills.  Or maybe 8-9 grunts killed themselves via poorly thrown grenades, etc and that's why I had less than 120?  In other news, today's challenges are very tough IMO. "