I had a game last year with my friend and his buddy that I had never met before. It was the two of them against with 1000 points against me with 2000 points. Normally with 2v1 and even points, I would stipulate that both sides use only one Force Org chart to keep things even. Not doing that opens up the game for abuse (this was back in 6th before the Unbound nonsense), but my friend was a classy guy and I assumed that his friend would be classy.
I was wrong.
In 1000 points this guy brought a cheesy DE netlist with three Voidravens and the rest was full of Warriors in Raiders with wargear that lets them reroll hits. This violates almost everything that I stand for in gaming. The flyers made up fully 1/2 of his army which flies in the face of The Warrior's Code. Taking three of any one thing is decidedly spamming and to do it in 1000 points is beyond the pale.
What this army says is to me as a first time player is this: "To hell with you. I don't care if you have fun. I designed, bought, and built this list to be as competitive and cheesy as possible with no consideration to how they are to play against. Winning. Winning is all that matters to me. Go die on a 3+ with a re-roll."
Before he finished deploying his army I had already decided that I would never play him again. His message was received loud and clear. I like a competitive opponent but would rather a good general than a good list builder.
This is a social game unlike almost everything else in our modern world. You can play Clash of Clans or World of Warcaft and still be a terrible person and misanthrope. You can't play 40k and hate everyone. If you do you are going to spend a lot of time admiring your collection and not a lot if time rolling dice.
That being said, you also don't have to like everyone. Your time is valuable and there is no need to waste it on people that you are not going to enjoy playing against. Winning isn't everything, but getting thrashed for no reason is not enjoyable for anyone (unless you are into that sort of thing).
In that way, it is just like dating and your first game is your first date. The best advice to get on a first date is be yourself. In your first game, the list you make should say something about who you are. I think of myself as fun, unpredictable, balanced, fluffy and a damn good painter and the first army you see from me should reflect that.
My biggest and best painted army is Blood Angles at 6,000 points at last count. It is also pretty flexible and competitive if I need it to be. I can run-and-gun with a Assault Squad in Razorbacks (a 5th Ed favorite). I can put a bunch of AV 12 and 13 vehicles and Dreads on the board. I can also put a lot of 3+ Sv bodies on the board and a lot of them with jump packs. In short, I can go for dis, or I can go for dat. Lots of options.
Here is the 1750 point list I decided on and why chose it:
Inquisitor, Terminator Armor (with Daemonhammer), Psycannon, Psyker (Divination)
I started my list here because I have wanted to play an Inquisitor since the new book came out. I made this guy out of Grey Knight Terminator with a Space Wolf head swap. The model is simple and pretty well painted. It is also a slightly unusual ally without being cheesy in any way.
Land Raider Crusader, Multimelta
The only down side to models in Terminator Armor is you have get them into battle somehow. They can only ride in a Land Raider or Deep Strike. My LR is well painted and magnetized.
Terminators x6, Heavy Flamer, Chainfist
Now that my Inquisitor has a ride, he needs some friends. I was going to put him with an Assault Squad but I wanted something a little more multi-purpose. Whatever power Divination gives me, the Terminators will benefit from in assault and shooting. I added in the extra guy because I had some points left over at the end. The Termies are very well painted if a little old.
I needed something that is anti-air and this is all I have. I have it Multimeltas and Lascannons to deal with anything in the air. I didn't have anything that I wanted to put in it so it is just anti-air. It could pick up a Dread or a Marine Squad if they get in trouble. The model is also spectacular.
Chaplain, Jump pack, Meltabombs
Now it is time to start making my real list. My first instinct was to use a Librarian to dominate the Psychic Phase, but my heart will always belong to Chaplains. If they get a charge off, it is totally worth it.
Assault Squad x10, Powerfist, Plasma Pistol, Meltagunx2
Now my Chaplain needs a posse and I can't think of a better crew to roll with than 10 kitted out Assault marines. They are the best friends a Chaplain could have. My Assault Marines are all converted and very well painted.
Assault Squad x5, Power Weapon, Meltagun
Assault Squad x5, Power Weapon, Meltagun
I love this thing. It is awesomely painted, tough and deadly. In every game it soaks a ton of firepower and never lets me down.
Drednought, Multimelta, Power Fist, Stormbolter, Drop Pod
For the points, you can not beat the disruptive ability of a Dread in a Drop Pod. First turn he is in your base killing your dudes. It is one of my favorite tactics and it says a lot about me and how I play.