Stompy, like Elves, is one of those archetypes that lends itself extremely well to variation. Sure, it's (mostly) just a dumb aggro deck, but with it you can go 1-2cmc only, go all in on counters, go all in on speed, and try many other things. Today I'll be exploring a few of the routes that can be taken.
To be clear, you might be lucky to do well with these decks in a real tournament. At least one of the ideas here has been implemented in a tournament setting and done well, but the primary goal is provide you with ways to play Stompy with your preferred twist, whether because the stock list doesn't interest you much, or because you want to mix it up for awhile. If any those ways happen to be competitive (and they do try to be, within their means), so be it. Onto it!
(Disclaimer: none of these lists have sideboards. Use the stock list sideboard as a starting point and go from there.)
This version values evasive creatures above all else, and sports a low curve, the idea being to get the absolute maximum amount of damage in as quickly as possible -- no grinding or creature wars, here, just running a load of creatures at your opponent's face and pumping them up a ton.
Sheltering Ancient adds some risky but potentially very explosive fun -- his downside matters less since we're very quick and their guys won't be able to chump block basically ever. Turn 3 kills are possible with this version, although likely rare.
The major downside of this list is all of your dudes excepting Ancient are vulnerable to every red removal spell in the format, though this is offset some by the high amount of pump spells (one of which is "free"), and the cheap cost of the creatures, meaning you can just keep cranking out dudes quickly and not be hurt so much by removal.
This is similar to the Evasion list in that it sports a very low curve. The difference is it excludes 1-drops in favor of more double green creatures, which means Aspect of Hydra is much better here. Also, it drops a couple of Ancient (which is less good in this version) for a couple of Battalion (which is better in this version). Finally, we use Aether Vial for added speed turn 3 and beyond and improved game versus removal and counterspells.
This is the "balls to the wall" aggro approach in effect. If you like Burn or those Izzet Blitz decks, this operates quite similarly. It's basically the same as the Evasion list, except it values speed and raw damage a little more than evasion.
Persist Stompy aims to maximize resilience while exploiting Life's Legacy and Phyrexian Soulgorger as much as possible. Incidentally, we get some added game versus aggro decks (particularly Burn), by running a playset of Finks.
More Incarnations of Stompy
The fun doesn't stop there: you can try exploring counters, the graveyard, hexproof, and many more aspects of Magic to produce other Stompy lists. I believe the ones above are likely the most competitive out of what you can do, but who knows -- Modern is so large, there's always more ground to cover. Enjoy!