I would terraform Venus if it were possible, as it is generally the closest planet to us and therefor would require fewer resources to travel to.
Well, there are multiple.
Assuming you are talking about the hairless cat owned by Dr. Evil on Austin Powers, I found it a hilarious alternative to the normal parody of the fluffy white cat owned by a villain.
Assuming you are talking about the cat owned by Kel-somethingorother in World of Warcraft, I have no opinion on him. Other than it was amusing at the time.
Quite the question here. Thing is though, every feature of Halo can be argued to be great features or horrible features depending on one's personal preference.
Personally, I have a small list of what I consider to be the best additions to the "Halo Experience" throughout the years.
1. The Two Weapon System: Having a primary and secondary weapon was not entirely unheard of, but at the time that Halo CE came out having an assault rifle and a sniper rifle simultaneously while being able to easily switch between the two was. Halo wouldn't be Halo without this little feature, which has since become a standard in Multiplayer FPS games.
2. Online Multiplayer: In many people's opinions the ability to connect more than one console together (either via LAN or XBL) is one of the greatest things to ever happen to Halo. I agree with them.
3. Balanced Maps: Halo got a cult competitive following because of this feature. Early Halo maps tended to be very balanced, whether they were symmetrical or not. If there was an awesome weapon on one side, there was an awesome counter on the other.
4. Vehicular Gameplay: Halo was one of the first games I have seen with both vehicular and pedestrian gameplay during one match. Running around while other people were in tanks used to be a crazy thought, until Halo brought the ability to take on vehicles while on foot into the mix. They started out with Banshees and Scorpions being the primary heavy vics, and then just kept adding more awesome vehicles.
5. Sprint: This one is definitely contentious, but personally when I was playing Halo 2 and 3 all I could think about is how long it took to get from point A to point B while on foot. It was pretty common to waste a warthog just to get to the point you wanted to on the map first. Sprint allows for more fluid movement around the map, in my opinion, and also makes things more interesting with the energy sword.
6. Fileshare: In Halo 3 the fileshare had to be my favorite thing of all time. Even when matches were taking forever to connect, you still had something to do because accessing a user's fileshare was as simple as pressing a couple of buttons. In the fileshare you could view their photos and get a better picture (ha) of who you were playing with or against. It was also good for some chuckles, as many of the photos were downright hilarious. Halo 3 definitely had the best version of the Fileshare system, and I wish it would make a comeback.
7. Competitive AND Casual playlists: This was something that was most noticeable in Halo 3. Generally speaking, there are two types of Halo Online Multiplayers. Competitive players and casual players. Halo 3 did it's best to accommodate both groups without alienating anyone from either group. There was a ranked playlist specifically for competitive gameplay, and an unranked playlist specifically for teh lulz. That's something that all games need, and Halo needs to bring back.