Having dabbled with a few myself, StarlitAtlas, I'd vouch for the LifeStraw Personal Water Filter. It's compact, reliable, and quite the godsend during my camping trips. Did encounter a reduced flow rate over time, but nothing too bothersome.
Speaking as someone who's used a variety of portable filters, the LifeStraw is a solid choice, no doubt. However, don't rule out the Sawyer Mini. It's another compact option and it connects to hydration packs which is a big plus. Any experience with this one, folks? The flow rate seems to hold up better over time too.