That's a hornworm.

From the FAQ:

Tomato Hornworm - are 3-4" long green caterpillars with diagonal lines on sides, prominent horn on rear end. Eat foliage and may take bites out of green fruit. Tomato hornworms are the larvae of 2 large moths: the Hawkmoth and the Sphinx moth and overwinter in the soil in the pupal stage. Adult moths appear in late spring and lay single,
pearl colored eggs on the undersides of plant leaves that hatch in about a week. Larvae feed on foliage for about a month before they enter the soil and pupate. They can be difficult to spot as coloring matches plant. Look for them on the undersides of leaf-stripped branches. They can easily be hand-picked and destroyed or if infestation is severe, use Bt (Bacillius thuringiensis) dust. Braconid wasps will kill these caterpillars by implanting rice-like eggs on their backs and Trichogramma wasps parasitize the eggs.

Here is a link that might be useful: FAQ - what are the common tomato pests?

That's a tobacco hornworm. If you only find just 2-3 on as many plants, just leave them be. They will not kill your plants and you can clip off strippd stems to allow more new branching and possible fruits. the big caterpillars don't eat ripening fruits but will occasionally bite a small green one. Nowhere near the type of damage caused by yucky slugs.

If you find more than 2 of these cats per plant, you may want to either place the extras on plants with no cats at all, find a wild nightshade weed to relocate them to, or just kill it. I don't recommend more than 2 hornworms per large tomato plant. I don't ecommend just killing them all for the very fact, they WON'T kill your plant. The moths are in fact, beneficial, too.

Another option, yet, is captive rearing. It's a lot of fun if you like bugs and it gives YOU control over which leaves to feed it.

Well if he wasn't causing any damage I'd leave him but he's on one of my ananas noirs and I noticed holes in the fruit and one looked eaten clean in half. So I picked him off and threw him in the woods. Don't have the stomach to "squash" things. :)

Ew I can't see even touching it. But it is cute though. I got one of these last year and it was covered in eggs. Just left it and that was the only one I saw. I didn't see any damage to my plant either.

Huh? I thought any boy would not mind touching a harmless little caterpillar! LOL! Actually, the tobacco HW's are quite soft and even slightly fuzzy. Very fun to hold!

Get that thing outta there - it will eat your whole plant fruit and all.

It won't eat the fruits, but may bite into the little green ones.