Is it a cheap shot in D&D to cast magic missile on a wizards familiar?

Cheap shot is relative. What one person considers “cheap shot” another may consider “fair game”, or possibly beneath even noticing at all.

Cruel moves… well, a bit of that depends on the gaming system. In Shadowrun, if you can’t think of at least three different bits of nastiness to do on each person in the room, then you aren’t going to last long in the shadows. And if you play Paranoia, then you not only have such plans, but actually execute them (ideally executing the target as well) before they do the same to you.

By those standards, D&D is pretty tame and thus actually requires one to think a little more outside the box to avoid being cliché. I mean, unless you’re a spell-user or psion, your options are very limited whereas even a baseline Homo Sapiens Sapiens can mess with people in many ways. (Homo Sapiens Ingentis (“Trolls”) tend to be less imaginative, but have the size and strength to do it the D&D way.) And since the very nature of a shadowrunner’s job is based on “playing dirty”, it’s a good thing that 2075 offers more options than anything you can do in straight High Fantasy like D&D.

Among those options are…

- Stench spell + Quickening metamagic (“Quickening” makes it self-sustaining so it won’t dissipate as soon as the caster stops concentrating.)
– Hack GridGuide™, the central traffic guidance network, to make their morning commute… interesting.
– EMP grenades on hackers/riggers using hot-sim VR. Kevlar won’t protect against the brain-burn of “dump shock”.
– Spoof a commcode to match a device in your target’s PAN (Personal Area Network), do something GOD (Grid Overwatch Division) would disapprove of, and wait for Convergence. At the very least, the device will be bricked by 12P damage. Also, their physical location will be given to the owners of the system you did whatever you did who are then free to respond it whatever manner they deem appropriate. It works best if you do it to a high-security system owned by a megacorp know for their sense of humor like Aztechnology (blood magic) or Saeder-Krupp (their CEO is a Great Dragon).
– Tell Tanamous that your target has Type-O organs; Tanamous is a “organlegging” operation. Where the Mafia may break your kneecaps, Tanamous will surgically remove them intact and sell them to a third party… possibly without anesthesia. And since medical resale is their primary source of revenue, your target won’t even need to owe them money to get a visit from one of their professionals like you would with most organized crime syndicates.
– When you find someone who is astrally projecting, move their body. For added fun, hide it behind a ward. Don’t forget to sell the soulless meatsack to Tanamous after the spirit dissipates a few hours later.

Note that of those six, only one of those requires magical talent while two can be done by a Mundane with the right computer skills and three can be done by anyone? And that’s just a few minutes worth of ideas; imagine what one could do if they actually spent some time trying to think of underhanded things to do to those who inconvenienced them!