TIGER, tiger, burning bright,
In the forests of the night,
What immortal hand or eye
Could frame thy fearful symmetry?
-Wm Blake, "The Tyger"
In the real world, Bengal Tigers (the most common type) clock in at about ten feet long (with tail, 6-7 feet without) and can weigh close to 500 pounds. That's a big kitty!
Tigers are also known for being one the more likely man-eaters among large predators. While there have been numerous fictional stories about such specimens, it is true that some tigers start preferring "long pork" for their meals.
Okay, on to the gaming stats, etc.
Tiger (from Moldvay)
No. App: 1 (1d3)
Move: 150' (50')
Attacks: 3 (claw/claw/bite)
While they normally are solitary, it is possible to encounter a few at once. One is probably enough to give a low to mid level party a bad few rounds, or even a fatality.
Tigers prefer cooler climates and wooded lands (according to Moldvay). "Cooler" as opposed to the lion's veldt, I expect. Fun fact: They appear in Cook's wilderness encounters on the "Inhabited" table! Staying close to the food, I expect! In fact, they appear on three different climate tables: Inhabited, Woods, and River. Oh, yes. That's another fun, real-life factoid about tigers: They like water and can swim (even submerged)!
Diving for a tasty snack.
(He's looking that ticked-off because he's pinching his nostrils shut
and keeping the water out of his ears. Still, eek!)
The monster description explains that the tiger's stripes help it hide, and in the woods the creature surprises on a 1-4! With its THAC0 of 12, there's a decent chance this thing is hitting for 4d6 damage before anyone knows what's happening. If your PC was the lucky one bringing up the rear, you better hope it doesn't gain initiative.
Fortunately for the PCs, this thing is just a normal animal. It would be scared of fire, and more interested in a meal than a melee. Its morale isn't great, so it would probably retreat under concentrated resistance. It's fast enough it will probably get away to lick its wounds and come follow from a safe distance, too. Its six HD means a Sleep spell isn't catching it, and it can probably survive a little damage before having to pick fight or flight.
As a GM, I see using this critter in nasty ambushes, causing party attrition. A hireling or pack animal killed. A PC badly injured so healing spells are used up. Heck, this thing roaring out among the trees might spook any riding or pack beasts into fleeing; preferably with valuable supplies on their backs!
A more nefarious scenario might be the classic "evil druid" with several of these things under an Animal Friendship spell.