Oh...I haven't been keeping up with them, but Steripen actually does have a bunch of other versions, including natively rechargeable Li-ion options. Cool. Since I'm all invested in the 5v standard, & solar stuff...that's a good option for me.
Vin has a good point. And in addition, any recommendation comes with a slew of other assumptions too. A general recommendation has a long trail of caveats.
But...if pressed...purely for the purposes of purification, in light-duty foreign travel and outdoorsy scenarios, with minimum fuss about batteries, charging, etc, the "SteriPen Classic 3", a pre-filter, and a wide-mouth Nalgene type bottle, with a set of primary (disposable) Lithium batteries in the unit and another set of batteries in the backpack makes for a pretty convenient, always-ready-to-go arrangement.
That covers alot of ground, and offers the convenience of a protocol that can be executed well in less than 3 minutes with little effort. Small footprint in your backpack. You have the option to switch to AA Lithium or NiMH rechargeables which are likely also the same ones you pack for camera flashes. It also scales reasonably well. (try filling your 10L dromedary or 5gal water cube with a traditional pump filter, and you'll very quickly be reaching for your backup chlorine dioxide tabs).
The only real vulnerabilities you have are fine turbidity, and heavy metals, and sloppy execution of the protocol.
There are ways to minimize risks from those vulnerabilities, and anyone aiming to use one of these ought to get familiar with those caveats. But it's a decent way to go when you're like me and pound through water at an extremely high rate while hiking. I can easily make 3 liters disappear in less than an hour, humping through steep climbs w/ a pack on my back. And most of the time, I'm not even packing the purifier for backcountry use. Most of the time, I'm packing the thing for use in less developed countries, where I don't trust the tapwater to agree with me.
It still won't help if you choose to eat the raw ceviche though...which I did...in Mexico..regrettably. It was delicious. But boy did I regret it.