I prefer not to ride in the rain but sometimes you can't help it when commuting. I almost always wear sunglasses or other eyewear to protect my eyes and see clearly. However, when it's raining hard or foggy, I sometimes take them off. I also keep a bandana handy to wipe off my glasses when they get wet.

For handlebars, I have found that cork tape is still grippy when wet, and the same is true for other types, such as Lizardskins.

Regarding tires, there are various brands of tires that are marketed for having better traction on wet roads, such as Continental GP 4 Seasons, Vittoria Rubino Pro Tech III, and many others. I have ridden dozens of different kinds of tires on wet roads and have not noticed huge differences, but I slow down and ride more cautiously, particularly when cornering.

Fenders will help more than anything when riding in the rain. I have found that rain jackets can be very effective in cooler temperatures, say below 60 F. However, in hotter temperatures you might get as wet from sweating as you would from the rain.