One of the attorneys at my firm asked about giving a logo'd promotional item as part of a holiday gift to a client. My advise in this matter is simple: Not the best thing to do.
During the holiday season gifts from attorneys to clients (or whomever) should be gifts acknowledging the relationship and hopefully friendship. Introducing a firm's logo is definitely a business development tactic... Not a thank you for the relationship we already have. It's true that service providers to law firms send over all sorts of logo'd mugs and mouse pads as "gifts" when in truth they're hoping to have little billboards spread throughout the office. Once again, tacky.
One final question if you are not yet on my side of this issue. Are your clients only worth what you give away for free the rest of the year?