What class? For me, for co-op?

Vanguard.

It is the most skilled class in any videogame period.

SKILL

Every party needs an asari, not just an adept specifically the asari, and an infiltrator. If those two are covered, play whatever. Go for the soldier or sentinel. Their powers kinda suck, so you can carry the heavy weapons into the fight and lay down plenty of support fire. A maxed out krogan sentinel gets something like 1600 shield and 1400 health, you can stay alive longer than anyone else, could help in getting a revive or that last objective.

Or, yanno, be a vanguard and a total detriment to the team, always going down every 5 seconds and oh, hey Bunny.

Yeah if you're going for a support class, be a Sentinel. With the tech armor, you can survive longer. On top of that, you can use your tech and biotic powers to support whatever is going on, no matter what enemy you're facing. 

I have to chuckle, every response so far has been a different class :lol:

I have a maxed Adaept, Soldier, Engineer and clost to a maxed Sentinal.  By far the Sentinal has been my favorite class especially if you can get the Turean Sentinal.  He has Overload which is awesome for Geth (which you fight like every other game since the balance change ) but it also is good on humans to overload their guns and stun them.  He has Warp which when leveled  up you can pick an enhancement that as long as the warp field is around the target, anyone who hits them with bullets or powers causes 15% extra damage.  If you're looking for a support power, that's pretty bad ass.  One of his level up powers is 20% extra headshot damage, you get any gunw ith a scope on it and it's easy to headshot, it's even pretty easy no-scope.  Combine Warp's 15% extra damage plus 20% extra headshot damage and you're killing shit left and right.  And last but not least, he has power armor which will save your bacon if a cloaked Geth Hunter or a Husk end up on your flank and surprise you, you can overload it to stun/damage them or even kill them if it's maxed out Plus it provides a little extra protection.

I'm playing the classes in order to max them out for Gold runs so  haven't played Infiltrator of Vanguard yet.

Sentinel is a good choice. The Turian sentinel when you get it will have tek armor, warp and overload. All bases covered and combining overload and warp do some great tech bursts. Also only equip one weapon. There are plenty of ammo crates lying around to keep you restoked. The big cooldown bonus from carrying little weight in weaponry is a major bonus.

Also can never go wrong with adepts and engineeers.

Like taco said the Asari is great for stasis. but as this power is only useful when  used properly its best to wait to fool with that till you have mastered another class. The infiltrater is another advanced class. The best one by far is the salurian. Oh gimminey he has skills.

That Turian Sentinal has saved my bacon many times and I like it for all the above reasons. Another feature the job has is recoil reduction which helps getting off a second and third shot.

Vangaurd(any race) is a fun job to play but like everyone notes, it is a paper tiger. Same with an Asari or Drell, in my op, they just can't take a ton of damage before they go down.

You said you play the game casually to have fun. I don't think I would have alot of fun laying face down dead alot. Try one of the tougher jobs and try the Krogan or Turian. Maybe you would like it!

Honestly I think infiltrator with a good snipe is the best overall class. Spec'd out right you can one shot kill reg enemies including nemesis, etc even on silver. The javelin fucking shreds shit through cover, I have killed 4-5 enemies from one bullet on multiple occasions. But if you have shitty sniper rifles I'd avoid tat class until you get something decent. Also the infiltrator is the ultimate ninja reviver and objective capper.

Heh. Yeah the great thing about Mass Effect is that you can pick one class and play a certain way and then come back as a different class and play totally differently. It's all up to you and how you want to play. 

I'm also a big fan of the infiltrator. Even with a weak sniper, using the cryo + headshot combo you can still 1 hit kill most enemies. And I've seen strategic use of tactical cloak finish entire waves solo more than once. 

Every room I go into seems to have some dude whose a lvl 25 using a lvl 14 Infiltrator with a Mantis II. So I've got to switch to a Turian Sentinel or Krogan soldier just so I can be a damage sponge because lord knows I'm going to have to do some of the objective work myself and get no help with the brutes until it comes time to steal the kill. 

My advice play a few different characters and try them out. Don't just run one character up too high because your weapons will suck. You won't earn enough xp to buy the good packs. Play a few styles and the bronze wins will level them up quick. In the early going you'll have 3 or 4 characters in the low teens and you'll start to add some veteran pack and maybe a few gold unlocks. It's also nice to be able to change to an alternate character in case your room has somebody like the above who's is keen to try out his brand new Widow.

I unlocked a Quarian engineer the other night, and I'm loving it.  My engineer was up to 14 anyway, and the turret really helps.

I think Human Engineer can be a good support class to get aquainted to the game because you can hang back and use overload/incinerate to help drop shields/armor.