Have a baby bottle filled with candies like M&M's or skittles. Have each guest write down on a piece of paper their name and how many they think are in the bottle. You can have them take guesses as they come in. Whoever gets the closest to the right number, wins the bottle of candy!
I know a great one for the guys who want to participate in some games! Get some baby bottles and fill them with soda and have them line up and see who can chug them down the fastest.
Have a diapering contest, get two teams and have them line up and see who can diaper/dress the baby the fastest. Winning team gets the prize.
Have everyone partner up and give each team playdoh. Have slips of paper in a container and draw out a piece of paper that will have a baby item listed on it. Walk around and show it to the team member who will be sculpting the item. The other person who guesses it first wins. Do about ten of these and tally up the points to see who got the most points. Examples can be: bottle, pacifier, high chair, carseat, etc. It's amazing how fast they'll be able to guess!
A lot of guys may prefer to stand back and observe than play baby shower games, but the ones I suggested most guys will have fun playing.
Great door prizes, or prizes for winning are candy bars! Guys would prefer candy bars over the typical baby shower party favor any day.
I have some more baby shower game ideas on my website:
http://www.bumblebeebabyboutique.com
I also make diaper cakes for baby showers if you need a great centerpiece/ gift for the mom!
Good luck with the babyshower!