For trouts:
  CDs by bearded free software luminaries
  The Eye of Argon
  Trabants
  Vashta Nerada
  XML
  ZALGO
  acorns
  albatrosses
  amontillado
  ash
  aque regia
  bananas (explosive)
  bananas (presumably non-explosive)
  barrels (incl. casks)
  baskets (prefilled with deplorables)
  bears
  bees
  beetles
  blood
  blue meanies
  bobcats
  bombs
  bones
  bricks (incl. breezeblocks)
  broken firewalls
  bubblegum
  bullets
  burgers (cheap ones)
  butter
  cactuses
  cake (of negative utility, like it's irradiated or something)
  camel fleas
  capsaicin
  carbonite
  carnivorous gerbils
  carrots (organic)
  chains
  cheese
  chips (embedded mind control devices)
  coal
  coca cola
  cockatrices
  crazy royal hats
  custard and custard pies
  deckchairs
  drugs
  duplicates of people (some of them antimatter)
  ebola
  eels
  elephant dung
  elephants
  engine oil
  explosives
  fake RAF moustaches
  fish fingers
  flapjacks (triangular)
  flying monkeys
  fridges
  giraffes
  glasses
  glue
  green ink
  grenades
  guppies
  hair styling tips
  half wasps
  hydrogen bombs
  iguanas (frozen)
  jaffa cakes
  jam
  jelly
  jimmy wales portraits
  keas
  lamination film
  laxatives
  lemons
  lions
  liquid nitrogen
  lizards
  luxury items
  marmite (lots)
  metal gorilla statues
  midges
  milk (sour)
  mines
  mongols
  mooses
  nails
  napalm
  natto
  non-explosive banans
  not dogfood (trouts provide it)
  novels (specifically by Louise Bagshaw)
  obsolete modems
  octopuses
  oil
  ominous boxen
  oranges
  ostraka
  paint (blue)
  paint (gold)
  paint (red)
  paper
  pepper spray
  pickelhauben
  pineapples
  pills
  plutonium
  pointed sticks
  poison
  porcupines
  potato eyes
  puns
  radiation
  raisins
  records
  red noses
  replica cathedrals
  rose petals
  rubber tubing
  scorpions
  several kinds of fish, of various quality grades
  sheep
  shivs
  shoe polish
  shoes
  shrink-wrap
  small boxes
  soggy clothes
  spiders
  spoons (wooden)
  staples
  statues (of Margaret Thatcher)
  t-shirts
  tar
  tattooing ink
  tennis balls
  the head of Alfredo Garcia
  thumb tacks
  toothpaste
  tractor fuel
  treacle
  trolls (female)
  ukip application forms
  varnish
  walls
  weasels
  whales (🐋)
  wheelbarrows
  whisky
  windows install media
  windows phones
  woodworm

For flirts:
  .xxx domains
  a batman outfit
  a club  
  an iPad
  archiepiscopal teddy bears
  bacon
  booze
  bottles
  bricks and mortar
  busses
  calling birds
  camels
  candles
  cassette tapes
  cat pictures
  champagne
  cherries
  chocolate sauce
  chocolates
  chrome makeup
  clotted cream
  cochineal
  dresses
  drummers
  fish
  flour, eggs, sugar, butter, milk
  flowers
  galeri
  geese
  gold medals
  gold rings
  golden syrup
  guano-encrusted Atlantic islands
  hairdye
  hard disks
  hens (french)
  honey
  hundreds and thousands
  iPads
  jam
  ladies
  last rolos
  lenses
  lords
  lubricant
  madeira
  maids
  milk tray
  moose
  not coffee (trouts provide it)
  paint
  partridges
  pear trees
  pencils
  pipers
  pizzas
  ponies
  porcelain sunflower seeds
  porn DVDs
  purple clothing
  red lightbulbs
  red roses
  rocks
  sandhoppers
  sloths (juvenile)
  spoons
  swans
  sweet nothings
  tattooing ink
  tea
  tinsel
  transparent clothes
  turkish delight
  turtle doves
  underwear

For both flirts and trouts:
  blancmange
  condoms
  cookies
  ducks (real, also rubber + huge)
  kittens
  paint (purple)
  paper
  pink dye
  vuvuzelas
  weedkiller

For slashes:
  .xxx domains
  condoms
  DVD blanks
  baby name books
  bad scripts
  bubblewrap
  condoms
  copies of the kama sutra
  glue
  hats
  marmalade
  money
  pencils and paper
  pyjamas
  underwear
  violins
  
For slashes and trouts:
  mice

For slashes and flirts:
  valentine's day cards