I wish I'd seen this post at the time it went up. This is an obsession of mine! My current favorite for deepthroat "practice" is the Noches Latinas Realistic Cock
. I have the massive 8" version (and yes, I've learned to deepthroat it completely!), but it also comes in a more realistic 6 1/2" length. It's the most realistic "pseudo-penis" I've ever seen/felt.
I can think of only one better way to overcome your gag reflex--and that would be by practicing on the real thing. As a married guy with same-sex desires, but who refuses to consider cheating on my wonderful wife, the real thing is no longer an option. But the Noches Latinas is the next best thing.
My next dildo for this purpose will be the Jeff Stryker UR3
. Which will present quite the challenge!