I often favor handiness. Usually, my sims end up with a high level just from fixing things all the time, without ever really needing to focus on it.
If you just want to have some fun though, I might give Alchemy a shot. It's a pretty easy and quick one to train, and if you have access to the ingredients, or can buy the potions you can't make, you can definitely have some fun with it. The top of the skill permits you to change life states at will, so if you feel like being something else for awhile, it's the perfect skill. You can also use it to make friends instantly, or enemies. Goes well with gardening and fishing both. Oh, and you can use it to advance your career faster if you wanted to do that.