And for the last year, that has meant the LG Nexus 4.
The reasons for making your Android phone a Nexus are:
1. No crapware. Not from the handset maker, nor from the carrier. It's just like when you buy an Apple (AAPL) Apple product of any size or shape.
2. You get your software updates directly from Google -- not from the handset maker or the carrier. This means you get them right away.
3. Google's employees use Nexus. This means that if there's a need for a security patch or a desire for new functionality, a Nexus will get them as fast as possible.
4. Price. Presumably somewhere between Google and the handset vendor, a Nexus device is sold either at cost, or Google may even throw in a subsidy. This will save you $200-$300 for an all-cash purchase.
5. No SIM-lock, no contract. Choose from the cheapest pay-as-you go plans from any carrier, in any country in the world. This could save you up to $50 per month here at "home" in the US, and in some cases several hundreds -- or even thousands -- of dollars per day when you're traveling abroad.
The Nexus 4 was introduced on Oct. 29, 2012, and sales started a few weeks thereafter. Demand was high in relation to supply, and it took a few months until the backlog had been cleared. Google has sold out of the Nexus 4 now, but it is still selling at outlets such as T-Mobile, Fry's and Amazon. Cash prices range from $200 to $500, so be sure to check the terms.