Here are several ideas. I tried to keep them short and simple. Sometimes it worked, sometimes I failed miserably

. English is not my first language, so please excuse the poor spelling/grammar.
A Wasteland Night's dream:You stumble upon a strange camp in the woods. The inhabitants call themselves the Seelie Court and try to speak, dress and behave like the Elves we know from Fantasy Books or Shakespeare's famous play. They have even undergone cosmetic surgery to look more like the mythic creatures they try to embody. It's an odd bunch, fascinating and slightly pathetic at the same time.
Turns out they are a group of wanna-be Eco-terrorists and through conversation and/or sneaking around you find out, that their fanatic leaders - a couple called Oberon and Titania (of course) - have gotten their hand on a pretty big bomb and plan a devastating assault. Maybe something like destroying the biggest power plant in the region (to bring humanity back to nature) or blowing up the biggest meat processor near by.
You can try to talk them out of it, simply kill the bunch, rat them out to the target place for a nice reward, assist them if it suits your goals ... heck, you can even try to convince them to attack another target, something that would help you in some way. Maybe killing the power supply will open up a way to enter a place that was previously inaccessible. Lots of options there.
Freak-Show Murder:Just because I'd simple love to have a circus/freak-show setting.
You enter a town in uproar. You find out that a child has been brutally killed in the streets. The rip-cage is torn open, there are claw marks all over the body and fur in the wounds. The residents believe this must have been done by some huge beast and the mayor is quick to point fingers at the nearby traveling freak show, that just arrived a few days earlier.
An angry mob is forming and to deescalate the situation you offer your help to solve the case - maybe even threaten them with violence, if they don't listen to reason. Next you collect evidence (take a closer look at the body, the wounds, search the pockets, take a fur sample etc.), talk to residents, travel to the freak show and do the same. Just some basic police stuff, really.
In the end you identify the true killer. It was the son of the mayor, who did some unimaginable things to this innocent little child. The claw marks and the rest was just a cover-up by the son and his father (although you can't prove his involvement) to avert suspicion and put the blame elsewhere.
Of course, it's your choice what to do with that knowledge. Arrest him? It's a corrupt world and Daddy is rich and powerful enough to probably get him out of jail rather quickly. Kill the bastard right away? Daddy will not be happy with that and it might cost you dearly later. Kill them both or spread rumors and let the mob do the work? Keep it a secret to call in some big favors later? The help of such an influential man could be crucial at some point. Blackmail the mayor and be rolling in money? But do you really want the blood of the innocent freak-show folks on your hand?
NegotiatorHere's a rather simple scenario: A man robs a bank, but is unable to flee. In desperation he storms into a school and takes the children and the teacher hostage. Due to your rank, training and experience, your squad is asked to take over command in the efforts to free the hostages.
You learn that he's basically a decent man, but a combination of circumstances has led him to this desperate move. You can try to talk him out of it. You can try spiked food/drink if you have the right pills handy. If you have a sharp-shooter on your squad, he might climb a building and try to get a clean shot or you could simply storm the place and hope for the best.
Science and other drugsYou meet a sleazy salesman. Weapons, Ammo, Drugs, Information ... whatever you need he either has it in stock or can get his hands on it.
He offers you a deal: a permanent 20% discount on all his wares and some valuable information for free, if you get rid off one of his rivals in the drug-business for him. Competition is bad for business, you see? And he's just another criminal, so who cares? He gives you the coordinates and you'll find a shabby looking farm. But the outside is misleading, cause the inside is all high-tech, albeit a little chaotic. The owner is a scientist who basically does the drug stuff to finance his other project: he's trying to develop an artificial fertilizer strong enough to wrest some harvest from even the most barren land. It could put food on the table of thousands, maybe millions of people. Although it seems he's years, maybe even decades away from a breakthrough.
He's obviously not keen on dying so he makes you a counteroffer: some free stuff whenever you visit and 30% on all his wares. He also has a job for you and the pay is very good. He noticed that animals around a certain cave seem to be much bigger than their counterparts elsewhere. He figures it could help him in his fertilizer research, if he knew what caused their abnormal growth.
Unfortunately they are also much more aggressive than normal beasts, so he never came close enough to find out about their secret. He wants you to enter the cave and look for the cause of the growth/mutation. If you accept the job, you'll find a pond in the cave, with a luminescent algae carpet floating on it. You take a sample and bring it back.
The Professor is delighted, pays you the reward and starts with his research. If you visit him later, he hasn't found a way to put the strange plant to use with his fertilizer, but has managed to produce a very potent drug. Taking the pill will increase the aggression level, so the party member will have more action points and be able to dish out much more damage. At the same time it's highly addictive and there's a chance he will go berserk in battle and you will lose all control over him. So use at your own risk.