I have all three

Of them, the Wave is probably the most used. HOWEVER, I need pliers regularly. Paired with a nice pocket clip, it'll go with him without much trouble
If he's an outdoors kind of guy, it's really tough to beat the Fireman. Personally, I'm not a fan of soft serrations on my main blade, so I would go with the regular non-one hand opening version. Besides, you already get the serrated belt cutter
Now, I know a lot of people love the Trekker. I'm a fan as well, but I'll take the Fireman over it for two reasons. First, I like having a dedicated rope cutter/bread knife. Secondly, I don't typically carry a SAK without a corkscrew. I know, I know...who needs a CS out in the woods? Well a guy that brings a bottle of wine does

. Besides, the can opener can turn a philips screw. A T-handle philips CANNOT open a bottle of wine
If you are looking for a little less costly tool, Gareth's idea is great. The blast, Fuse, or Kick would be great choices as an intro to multi-tools without breaking the bank. You do lose the one hand feature, though.
Good luck
