I also seem to remember them taking several motorcycle adventures together. I remember assuming they were together and thought maybe Adam X was in the family too :)

Jeph Loeb was very subtle, but he brought it in every once in awhile. For some reason I can't upload any pictures, but in one panel from X-Force a long time ago, Shatterstar is fighting what appears to be Siryn (god I'm getting this wrong) he says "tag you're the one" and the commentary is that she has lost warpath, and he has lost rictor, and that both are too stubborn to admit that they may mean more than just friends. Loeb always planned to make them a couple, and they prob would have been ONE of the first gay marvel couples, but Loeb left before he could do it. In comes Peter David and he picks up where Loeb left off, in a much less subtle way :D

I can post some more scans of minor hints that we know are minor hints (later this week), because the writers have been fairly candid with what they were planning with this subplot, there was the nightclub issue and quite a few moments as a few posters above me describe. I think there is even a website dedicated to those moments that was created pre Pad written Shatterstar/Rictor. 

Interesting article on the subject 
http://www.afterelton.com/other/2009/12/rictor-met-shatterstar-peter-david-interview 
Also on a side note, anyone remember how casually stereotypical Rictor was back then? lmao he wanst speedy gonzales but really it was kinda....interesting :O