Seldom-Used Skills
As versatile as the list of skills is, sometimes it just starts to seem like there are only a handful that are really useful. This creates a very predictable formula for making a character, which can make the game boring, given enough time. In order to avoid this, I suggest throwing your players into situations where they need to rely on a skill, specifically one that is not commonly taken. This encourages them to invest in the more obscure skills, as well as creating a situation that will catch them off guard. Below is a list of the skills that are not invested in as much, and how they can be integrated into your campaign.
Animal Empathy: Strange mounts, unusual creatures, basically a ranger’s paradise. Have your players constantly encounter animalistic creatures, ones that the group would rather have just leave them alone. Have them attack at night for additional effect.
Decipher Script: Usually, if a DM throws a coded message into a game, he intends for it to stay coded until the players find someone who can translate it. Make the decoder a side trip, and offer to give the players a chance to figure it out themselves.
Escape Artist: This is an easy one. Throw the players in a dungeon with low DC shackles.
Innuendo: This is perhaps one of the more obscure skills. If you want your players to invest in it, you should first have your NPCs put some ranks in it. This works especially well in an urban setting, if your players are fighting a thieves guild, cult, or other form of organization. Have some meetings go on that the players can see, but use innuendo to code the conversation. Sure, the PCs can still figure out what the agents mean, but not without considerable effort, which could be saved with this skill.
Profession: This makes you practically no money, so many players ask why they should have it? Simple, it gives you connections. Need to get across the sea? If a player has “Profession: Sailor”, all he has to do is sell his services for a ride. Also, sea combat can be a really difficult challenge for parties that are not used to being at sea.
Read Lips: Another next to useless skill in most adventures, but all you have to do to make your players curse themselves for not having it is have two NPCs have a conversation in a soundproof room behind glass.