OK, this is kind of an awkward one from a UK standpoint. The whole definition of an IPA, on account of it needed to be shipped longer distances, necessitated a higher than normal ABV than what a typical ale of the time was, and that is still kept today - here it would be extremely rare to describe an IPA as a session beer. If over the pond you're brewing things in a similar style, but without the restrictions of knowing that if it is not drunk in the time it takes to ship it a fair chunk around the world, it'd be spoiled, that's fine - it's likely just for all intents and purposes different nomenclature at this stage. But in terms of our best ales in this sort of style:
Jaipur (Thornbridge, 5.9%) - Definitely not session. Definitely something that drinks easier than its ABV. Thornbridge are pretty darned good at what they do regardless of strength (their Wild Swan, at 3.5%, would probably be my pick where if forced to drink nothing else for the rest of my life). Generally perceived as citrusy, it is simply peak IPA. If you are ever able to get a special version of this, do so immediately.
I would say that if you are wanting something in a general ale style, and want a session ale, not that you will likely ever see it in the US (at least on tap, I think they may bottle it), then Oakham's Jeffrey Hudson Bitter (3.8%) is another one where if forced to drink nothing more until the end of days I'd say "yeah, fine"