This can be anything from the Elite line to body kits to mass-produced stefans, etc., but basically, what do you think are the most significant of advances in Nerf, how we mod, how we play, and how we have otherwise advanced as a community since 2006?
I think the most significant advances are (and why for those of you that are new to the hobby or this platform):
1. 18-round and 22-round stick magazines. Back in the old days of '06-'11, most mag-fed blasters could only hold six shots. 18-round mags and later 22-round mags were a huge deal, especially when most mag-fed blasters were still springers and had a slow ROF.
2. Flywheel blasters that feed from magazines. Before these, the fastest ones could shoot without belts, pumping or front-loading darts was the Recon, Maverick or Longshot. With flywheels and mags came the ability to rapidly reload and fire, giving close-quarter players a lot more of an edge and a solution to the inherent inaccuracy of Nerf darts.
3. The Elite line. In '06-'11, most Nerf guns were reverse plunger and engineered to be poor. With the Elite line, mod potential skyrocketed due to direct plungers and they shot much, much harder (up to 40 harder%) than their stock predecessors.
4. Drop-in kits. Don't want to go through the hassle of carefully Dremeling out your own bolt sled out of brass, hot-gluing coat hanger pieces to reinforce your bolt sleds and other various homebrewed solutions to modding? Well, now most people can "drag and drop" parts into their blasters and make them shoot much harder, with a minimum of tools and expense. And drop-in kits are EVERYWHERE these days, and companies are making entire kit blasters that one can assemble themselves with a screwdriver, hobby knife, Allen keys, and the like to get 200FPS Nerf blasters.
5. The Rival line and the Elite dart. The Rival line brought back the idea of foam balls being an ammo type that didn't suck and blow at the same time, while having a much higher muzzle velocity than dart blasters and much better accuracy indoors, while the Elite Dart bridged the gap between the older Suction Micro, Sonic Micro/Whistler, Streamline and other various types of darts. Not only that, but the sheer amount of things that Elite darts and their magazines could use spawned the Buzz Bee Elite-compatible darts and N-Strike compatible magazines, which effectively forced the entire industry (save for BoomCo because they're weird) to standardize on that style of dart. This gave us FVJ's, Kooshes, waffle-tips, Accustrike, Accufake, nipple-tip, Z-Patterns, Super Darts, etc, etc, effectively giving us free reign over what ammo to choose in what colours and nearly every Nerf gun in existence uses the same darts (apart from vintage blasters with their own ammo types, Megas, which are also standardized, as are Rival balls).