Loxodon Warhammer is an interesting card. To me, it is better than Umezawa's Jitte any fine day. Not because it is a better card, it's because it keeps a game long and interesting, or short and uninteresting. Multiple copies on both sides can cause the game to stretch on for hours despite it's inherent power to end games.
The result of having a Loxodon Warhammer on the table is about the same as having an Umezawa's Jitte or Sunforger on the table. It completely warps the game. People might think the Warhammer is less of a threat than the Jitte. It's actually merely less efficient. Jitte drops for 4 and Warhammer for 6.
It's still a clear and present danger on the table when it comes into play successfully. For starters, let us imagine it equipped to a 1/1 creature. This means it is instantly a pretty useful 4/1 with life gain attached to it when it deals damage. This 4/1 will most definitely become a martyr, so you've just paid the 3 mana to equip it to gain 4 life. Sacred Nectar does this for a one mana discount and without having to sacrifice a creature to do it.
Then, we look at it is I place it on, let's say a Dancing Scimitar. That would make it a 4/5 flying creature. Since a 4/5 flying creature is arguably far more difficult to terminate, it would probably guarantee me 4 life every turn, whether there is a blocker or not. Being able to play a Sacred Nectar for free every turn after the first is certainly a great deal, especially since it keeps pressure on your opponent. What is the moral of the story? Place Loxodon Warhammer on something that is difficult to kill.
Then ,we look at an innocent looking Dimir Infiltrator. Equipping that thin humanoid with this Loxodon Warhammer makes it into 4/3 unblockable creature. This completely changes the state of the game. For one, as long as this combination remains on the table, you are essentially guaranteed an 8 life point advantage every time you attack. How does this advantage come about? You attack with Dimir Infiltrator and deal 4 damage to your opponent. That 4 damage in turn becomes 4 life for you. Since he received -4 life, and you received 4 life, that makes a 8 life advantage.
Now, all I've been talking about it simply two cards. In truth, Loxodon Warhammer works well with many other cards, especially other cards which boost power and toughness, like Holy Strength, Unholy Strength, Moldervine Cloak and more. Even measly repeatable +1/+1 like on Ursapine and Shades can quickly turn the game into a far quicker game (or far slower game, depending on how disadvantaged you are). Anything which increases attack power will certainly boost the amount of life gained, and anything which increases toughness will keep your creatures alive longer to deal more damage and let you gain more life.
Of course, you want to look cool, you obviously want to gain more life. Using simple +1/+1 s just plainly isn't enough for you. How do you add to the already broken look of your equipment? Add more gain life effects. A good example would be the innocent looking Spirit Link. If you have been reading my blog posts about the prerelease, I mentioned that a Skyhunter Prowler with both Loxodon Warhammer and Spirit Link makes life gaining really look undercosted since the life gain doubled easily into a crazy 8 life per turn, creating a nearly impossible to reverse life advantage of 12 every turn. While your at it, have more fun - put another Loxodon Warhammer into the fray on the same creature. +6/+0 to a single creature isn't funny, and the double lifegain per damage dealt makes things even more warped. Imagine being swung at by an originally 0/1 Birds of Paradise, now turned into a 6/1, gain 12 life whenever this creature attacks. This easily compounds with every additional Warhammer on the poor small bird.
Another way to double your take it by using a creature with double strike (like Boros Swiftblade, for example). This works with Jitte extremely well (a lot better than the Warhammer ever will), but that doesn't mean that Loxodon Warhammer can't join in on the fun. After all, putting both on the same Swiftblade would give your opponent the fits.
The main reason I like Loxodon Warhammer better than Umezawa's Jitte is a matter of opinion. I have a few reasons to back my opinion:
1. Loxodon Warhammer works well with even the most basic of creature pumping abilities, spells, enchantments and so on. This means that once you draw the Warhammer, you can have tons of fun with the synergy it has with many, many other cards. I can't say the same for Jitte, since it doesn't have synergy with many cards but it is powerful enough on its own.
2. You can have multiple Loxodon Warhammers in play. This could mean someone is going to take a serious beating to death. As for the Jitte, it takes a lot more work to make it happen. Since you can add to the craziness, it's certainly a lot more fun, especially since you can be pulling on multiple life gaining effects and your opponent can be gaining life too!
Of course, I like the Jitte too. :D But that card doesn't need it's own post. The card speaks for itself.