Despite what I said about giving clothing as gifts, it's okay for a groom to give his groomsmen neckties. Same way that I'd discourage giving your guy friends jewelry, but giving your groomsmen matching cuff links would be okay. Groomsmen gifts fall into a special category that way.
Oh, whenever I read here on SF that someone's getting married, I have to ask - you're not having your groomsmen all dress in matching outfits, are you? Please, for the love of Dog, tell me you're not making that mistake, no matter what the bride and/or wedding planner want. You have one groomsman who is the size of Herman Munster. You probably have another who's on the short and slight side. It's unlikely that the suit and/or tuxedo which looks best on one, will also look best on the other. Moreover, in looking at old wedding photos, I've never, ever thought to myself, "I wish all of grandpa's groomsmen had been wearing identical suits." So long as the groomsmen are dressed in the appropriate tone, there is absolutely nothing to be gained from having them all match, and quite a bit of reason to avoid this.