A "sad" little game that I got to play was Gloom. (Yes, I like puns, and I think it is important to share them with the world.)
In Gloom, each player controls a family of soon-to-be miserable people. The object of the game is to make your family as miserable as possible... and then to kill them. Each turn consists of playing 0-2 cards and then redrawing your hand back up to 5 (if it was less than 5). The cards that you play can be on any character in play that is still alive - whether they belong to you or another player (but only the first card played can kill a character). Once one player has killed off all of the members of their family, the game is over, and the person with the most miserable family (only counting the dead family members) is the winner.
Gloom's first pro is its portability and ease of play. It is a small card game that can be explained in about 5 minutes or less (if you read the previous paragraph, you know most of the rules). Because of this, it makes it a good filler game for whenever you have a little extra time, wherever you may wind up (at an airport?).
The next pro to Gloom is in the transparent, stacking cards. I have seen this type of card elsewhere (in Hecatomb), but it is done differently and with less confusion in Gloom. Each of the cards is transparent, and there are 1-3 different modifiers on most cards. The modifier cards are placed on top of a character (and each other), and whichever modifiers are visible once the new card is played are the ones in effect. Therefore, if your opponent has a -30 on one of his characters in the middle spot, you can bring joy to his family member by placing a +10 on top of him. If this covered the -30, the +10 would replace the -30.
The final pro to Gloom is that the flavor text is quite amusing. I haven't read all of it, but the creators seemed to put some thought into the names of the cards as well as the characters. For example, the family that I played was a group of failed circus freaks such as the "Bearded Man".
The first con to Gloom is pretty obvious - not everyone will want to play a game about making people miserable and then killing them. More specifically, many people will not want to teach their children a game like this (of course, not everyone is this way, as my friends taught this game to their children at age 8). This has nothing to do with gameplay, but you should be aware of it when deciding whether you want to buy the game.
The next con is that the game isn't really all that complicated, and so it can become fairly repetitive. Every round will consist of doing very similar things - making your family miserable, bringing joy to others, or killing off characters. Because of this, it is important to not take this game seriously. It should be played as a conversation piece more than as a game itself. It can be fun, but it will not keep your mind very engaged.
Overall, I give Gloom a 7.0/10. It is a good little game, but I have several other card games that I prefer (like Lunch Money). If a friend brings Gloom with them and wants to play it, I will probably be willing, but I don't anticipate seeking it out.
If Gloom sounds interesting, you might also check out Jab: Real time boxing, For Sale, and Dixit.