Torchlight: Hack, slash, repeat!
If you took Rogue, NetHack, Diablo, Diablo II and Fate, threw them all in a blender, then strained the pure awesomeness out into a brand new game you would be sued for copyright infringement because Torchlight already exists.
Torchlight is the essence of a dungeon crawler made beautiful. The story is there, if you care, and it’s just fine. But we all know what we’re here to do: beat up monsters and get treasures. Somewhere down there are some big monsters, and waaaay down there is a really really big monster. Okay, got it, let’s go.
Torchlight lets you get right to business with a minimum of fuss. Choose a class: Destroyer (big guy with sword), Alchemist (little guy with magic spells), or Vindicator (girl with bows or guns). Choose a pet (dog, cat) and get to the dungeon. The first levels are just perfect: You’re in a mine full of little goblin guys that get flung backwards when hit them, dynamite you can use to open up rooms full of treasure, random spells and potions and piles of gold littered all over the place, mine shafts that pour forth hordes of spiders when you walk past, the works. Torchlight doesn’t make you slog through three or four levels before it gets fun; it’s fun from the get-go.
And it just gets better. Each class gains new skills and abilities, and has a wide enough palette that you can really customize the class to the way you play. For example, I played the Alchemist (spell caster dude), consistently chose spells that let me summon creatures, and soon had my own personal army beating up the baddies while I stood back and cast support spells. Meanwhile my friend was playing the Alchemist as a one-man artillery battery, hurling fireballs and laser blasts at the baddies, with no pets but his trusty dog. Have a favorite weapon that just isn’t doing the job anymore? Take it to the enchanter (perhaps his name is Tim?) and have him put a few spells on it. Now your awesome bow is an awesome bow that shoots flaming poisoned arrows! You’re good to go!
But what about these pets I mentioned? What do they do? Think of your pet as a furry four-legged Swiss army knife that cuts out the irritating stuff and lets you focus on killing baddies. For example: let’s say your inventory is full and you don’t want to go back up to town. Easy: just send your pet to town. They’ve got a pack and will sell your unneeded goodies then bring the money back to you. (Rumors of your pet charging a fee are unsubstantiated.) Love getting healed but hate casting healing spells? Your pet can learn up to two spells, so teach ‘em a healing spell. Wish your pet was a giant spider? Feed them a fish. (Yeah, I don’t know either. But it’s fun.)
Every angle, every detail of the game is well thought out. When you finally beat the Big Bad Guy you can keep playing through another set of randomly-generated levels, eventually turning your character into a small, wrathful god. When you get tired of that you can retire. Retiring means your character is no longer playable, but you get to start a brand new character as a descendent. This new descendent gets some cool bonuses, but the best part is the gift that you give the descendent when you retire: your heirloom item. This item takes on your character’s name (i.e. the “Flaming Sword of the Giant” becomes “Rock Hardhit’s Flaming Sword of the Giant”) and some stat boosts as well, and it’s awesome pretending that you are using grandpa’s flaming sword to come back and finish the job.
So go forth, adventurer. There is a great evil lurking. And defeating it will be a blast.

I won a copy of this game at PAX (thanks, Seattle Geekly!), and have been ITCHING to dive in. You know what? Screw daily word count goals! Torchlight is GO.
I can play while you write! IT IS A FAULTLESS PLAN
it’s a pretty ballsy game on the HARD setting. If I were to play again, I might take it down a notch.
That said, I would say that it lacks the tactical complexity and diversity of a modern Nethack game such as Stone Soup.
http://crawl.develz.org/wordpress/
I would humbly submit that nothing is as complex or diverse as Nethack et al.
I’ve been playing Rogue and Nethack off and on since I was ten, and I’ve never actually finished one of those games, although I have some cherished memories of some of my better deaths. (Here lies Nate: Killed by a rotten iguana carcass)
I think I like Torchlight so much because it is so tightly focused.