(Photo: BBC America) 
Your mission: You’ve been dropped on an alien planet. The terrain is grey and unforgiving. There are icy winds howling across what looks like a slate quarry in Wales (but is actually a place very far from there, in both time and space, honest).
You chance upon a supply shed, equipped with many items that could help you, should you find yourself under attack. And there’s a big bag you can put things in.
So, what are the key items you’ll need in order to be the most prepared for battle, given that you don’t know where you are or who you may have to defend yourself against?
Let’s take a look:
A mallet

Any kind of whacking hammer or blunt projectile will do, even an arrow, a knife or a frying pan, but the key thing to remember is that Sontarans – the great warrior race – will keel over if you can whack them in the probic vent (situated at the back of the neck) with something weighty. For some reason, Dan Lewis and his parents may have mocked the drunken citizen of Birkenhead who chose to have a go with a mallet, but it’s hard to think of a better weapon in hand-to-hand combat with the soldiers of Sontar. The Tenth Doctor might have stunned General Staal with a rubber ball, but really, to even hope to do likewise your aim has to be exceptional. It’s better to rely on something you can control more easily.
A gold earring

Any golden item should suffice, but it’s long been established that Cybermen don’t like gold. It messes with their innards. They may have upgraded over recent years to be less affected, but it’s still worth having a little gold something on your person in case you have to fend off a silver menace or two.
Having said that, you wouldn’t want to keep it in contact with your skin in case you run across the Animus (“The Web Planet”). That ancient being could use gold to control the mind of any living creature, even massive wasp-like bug rotters like the Zarbi. 
A bag of chips

This covers both the American and British definitions of the word “chip,” but what we’re really focusing in on here is the seasoning applied, and that’s very specific to the Brits, so make sure your interstellar supply shed has good links to the U.K., if possible.
Should you need to do battle with a Fendahleen, as the Fourth Doctor and Leela did in “Image of the Fendahl”, you’ll need the salt. They’re like slugs, can’t bear the stuff. Meanwhile, a traditional bottle of malt vinegar, as seen on the counter of any fish and chip shop in the British Isles, should be more than enough to dispose of any Slitheen (“Aliens of London”) you may come across.
Nailpolish remover

Any solvent should work just as well, but what we want here is some commonly available liquid that can melt the plastic form of an Auton (“Rose”). Or at the very least, cause their hand-guns to become sticky on the inside. A liberal soaking of nail polish remover would do the job admirably, although any teenage boy will no doubt also tell you that if you apply a naked flame to the end of the plastic barrel, you could easily pull it out of shape, or just melt the whole hand into big, and relatively useless, club.
A bottle of water

Leaving aside for a moment how perpetually useful and life-saving it is to have something to drink, the particular reason this bottle could come in handy is to do with basic hygiene. In “The Seeds of Death,” the Second Doctor, Jamie and Zoe do battle with a fungus that is very susceptible to a drop of water, and they win, using exactly that. It’s just like your mother always said, wash your hands!
And while we’re at it, the Pyrovile soldiers in “The Fires of Pompeii” also suffer with a very low H2O tolerance, although you may need quite a bit more, given their liquid rock form. Still, if you can grab a bottle or two, or have a canteen you can easily refill from a babbling stream, so much the better.
A trowel

Sometimes you can con a foe into thinking they’re defeated even when they’re not. For example, should you come across a gargoyle that has come to life, as happened to the Third Doctor in “The Daemons,” try a little cunning ploy with your trusty trowel. It’s a well-known fact (in Doctor Who lore at least) that gargoyles believe iron is magic, so if you wave your trowel and intone the magic words, “clokleda partha mennin klatch” – the first line of an old Venusian lullaby, which means, “close your eyes, my darling. Well, three of them, at least” – you’ll frighten him away. No, really, it worked.
And finally, if you can find it…
A canister of hexachromite gas

Granted, hexachromite is unlikely to appear in your shed, unless interstellar gardeners have been using it to kill off the reptilian pests chewing on their space tomatoes. But it is remarkably effective as a deadly weapon against both Sea Devils and their earthbound cousins, the Silurians.  The Fifth Doctor wiped out a considerable amount of them, just before they destroyed humanity, in “Warriors of the Deep.” And if that doesn’t work, try a sharp poke in the eye and run like heck.
Do you now feel prepared if you come across any Doctor Who aliens!?