We've tested a ton of backpacking water filters. However, for whatever reason, the LifeStraw personal water filter has an absolute chokehold on WIRED readers. The LifeStraw Personal Water Filter Is $10 TodayThis isn't the best water filter, and it isn't even the best LifeStraw. I also like the LifeStraw Go Series ($34, $16 off). The very first LifeStraw is cheap, light, and perfect for sticking in an emergency kit.