A few pieces of plastic can vastly improve the ergonomics and battery life of your controllers and portables.
Eons ago during the Playstation 3 era, affixing frequently sub-$3 plastic caps to your DualShock 3's marshmallow-y L2 and R2 buttons was basically enough to fix the most nagging complaint with that particular controller.
When I got my Playstation Vita I never even tried to hold it without the Nyko Power Grip. The shape of the grip is so intuitively and obviously better that I bought it before I got the Vita and installed immediately opening the box, not to mention it more or less doubles the battery life.
There's also a model of the Power Grip for the Vita Slim.
A more simple option for fixing the Vita's ergonomics is the PDP Trigger Grips (I don't know why it's plural). There's no battery boost with the PDP, but the fact that it's on sale for $6 today is what inspired this article.
The 3DS is the most desperately in need of some kind of grip or cradle. Battery life aside I've often remarked that it's the most uncomfortable device I've ever held. I bought the Circle Pad LL for my 3DS XL, and there are also several options for the regular 3DS, include this $10 offering from CTA that looks similar to the PDP Trigger Grips for the Vita.
We also recently covered some interesting new options for charging your new controllers, so check those out if you missed it.