When used, the effects of the tranquilizer gun work immediately and induce temporary unconsciousness in the enemies hit. The effects of this weapon are slightly stronger against humans, but it will also work very well on animals. This weapon will kill bats and spiders, but has no effect on supernatural opponents. It also has a very slow rate of fire and is inaccurate even at close range. Use the tranquilizer gun at close range and against stationary targets for best effect and accuracy. Use Lara's tranquilizer gun in situations where it can be used to slowly reduce the number of opponents she's forced to fight and then take care of the rest the old fashioned way.
In Tomb Raider Underworld, Lara's spear gun is obviously designed to be used in underwater environments in the game. However, in a pinch this weapon can be very effective on dry land. This weapon has close-range stopping power, will push your opponent back, and will briefly stun most of the enemy types Lara will face in the game. Unfortunately, the spear gun is really slow to reload, leaving Lara vulnerable. So don't reload this weapon once used, switch to something else.
The adhesive property of sticky grenades makes one of them absolutely lethal against all types of enemies, except the Yeti thrall, which will require a few sticky grenades to eliminate. Use sticky grenades to set traps for chasers or groups of enemies by sticking them to walls to offer groups of chasers or attacks. Lara is such a good shot that you can even use Lock On to target sticky grenades that have attached themselves to opponents and take them and surrounding enemies out at the same time.
Thor's Hammer can quickly dispatch all of the enemies Lara faces while playing the game. The Yeti Thrall and Natla will require more than one hit, but even these tough opponents will be eliminated when hit by Thor's Hammer. Thor's Hammer does have a relatively slow rate of fire, so enemies can close or shoot between your shots, but make use of the long range ability of Thor's Hammer and even this weakness is less of a problem.
Lara is not at her best in melee combat, but occasionally it will be necessary for Lara to take part in melee combat in order for her to survive. Use melee combat in combination with Lara's pistols and shotgun for best effect. She can easily move around and still take out all the bad guys. Lara's melee attacks also have a brief stun effect, so except for Thralls, you can use Lara in melee combat very effectively.
Any object Lara can pick up can be used in melee combat, grab a loose pole or crate and it can be employed as a very effective close combat weapon. This doesn't mean that Lara should carry around excess weight in the form of things she might be able to use in melee combat. Instead, use the objects in the environments.
Lara gets to ride a motorcycle during the Southern Mexico and Jan Mayen Island levels (See the Tomb Raider Underworld walkthrough for more details). Lara is such a skilled rider, she can even use her motorcycle to take out the bad guys. Direct, full-speed contact with an opponent usually results in instant death for Lara's opponent, and even donuts and power slides can inflict significant damage on her opponents.