One the the things that makes a city an environment worth visiting over and over again, is the people. The people of a city can do more to bring it to life than many other common elements used to bring unique designs to dungeons and wilderness.
Along those lines, assassins are something that springs to mind when I think of cities. In terms of where such inspiration might have originated from, in my youth, Raymond Feist wrote of Nighthawks, a group of assassins that worked in the cities and that Jimmy the Hand had to help a young noble struggle against. Another older write, Frizt Leiber had the Slayers Brotherhood, a guild of assassins in Lankhimar.
In more modern viewings, although still fairly old, one of the most popular assassins has to come from manga in the form of Lone Wolf and Cub. A series nearly thirty books long with many a tragic tale woven along the way.
Even Dungeons and Dragons fiction doesn't escape the long appeal of the assassin with one of the most popular (and loved to be hated by the internets) characters, Drizzt, having a rival, Artemis. The latter even carrying several novels of his own.
Assassins can make for clever foes or for nameless thugs. They can be used to showcase how seriously an enemy is taking the players, such as in the Paizo setting where Red Mantis Assassins may be hunting your party, as happens in at least one adventure path, or in older material such the Scarlet Brotherhood is known to use them such as in Expedition to the Keep on the Borderlands and other resources.
My own recent exposure to assassins and the tie in to Appendix N, where I try to keep what I'm reading, watching, and doing in terms of how it effects my gaming, would be Golgo 13, or at least the 12 episodes in one variation of it available for viewing from Netflix.
The problem with Golgo 13 though, is he's boring. He is set up as such a perfect sniper and killer that even when one of the other characters comes in and points out method after method of how the sniper must fail and cannot succeed or how the other character is some type of rival sniper and how he has laid out all of his plans, Golgo breezes through them.
This to me can be entertaining at times seeing the ultimate professional, but there is no build up or testing of the character's skill. There is no moment where the viewer is worried about the fate of Golgo. He's just so good that you might as well read the summary of the series and figure, "Yeah, this character's plan isn't going to work and Golgo will kill the target."
So that reminds me to keep things at least interesting for the characters. Keep them guessing at the very least. Try to have some sort of build up where
Thoughts on 1st game with new High Elves - Well that didnt go at all well. Up against Calebs Warriors of Chaos last night lead by a Daemon Prince and with 2 blocks of Knights and 2 of Juggernauts I...
41 minutes ago