Mine is 16 months too. Her current faves are:

• balls - she has 2 or 3 of different sizes and loves throwing/chasing them
  
• books - will amuse herself for ages, especially if they have "doors" to open
  
• little people farm
  
• tunnel from ikea - was a bargain and she loves sitting in it
  
• felt tips/crayons and paper
  
• washing up bowl with water and toys to "wash"/splash about in
  
  HTH

when my dd was 12m she got as a present a box with plastic eggs (i think they're Tommy and probably easy to find at Mothercare). they open-up and make squeek sound when pressed, ahve different shapes at the bottom to fit in the tray. it was her most favourite toy for at least 1 whole year. she also liked a tunnel and tent we got her from ELC and favoured playing with water (just put lots of plastic toys in a small paddling pool or a bucket and she'll be busy for a long time). she was very very interested in books (just like crumpet says) and cooking with me (well, sort of stiring), also musical toys were of much interest to her (piano, rattling toys, that sort of stuff). and toys that move on their own or make sounds when pressed (she had a favourite little plastic horse with batteries, incredibly noisy but she loved it) and stack-up blocks/cups. But she also loved playing with household items (safe plastic kitchen tools, or wooden ones, boxes of any type) and anything to fill up and empty. i remember getting her a lego set (the really big blocks you get in Woolworth) around 16-18m and she was thrilled with that too. I think the best ones were books though. Hope this helps a bit.

Mine liked:

Duplo lego
little people toys - garage, toys, housees
playdough
sandpit/water play
dolls buggies or trolleys with doll or teddy

all these are good as they'll play with them for years, my oldest dd is 4 now and still plays with all these. And they are all easy to find secondhand (car boot sales, school fairs) if you don't want to spend lots of money.

My dd has a little ball pool. She loves playing with the balls, you can get a bag of 100 quite cheap at tescos I saw. She has toys of her favourite characters such as Woody from Toy Story and Rockit from Fimbles. She likes playing with hoops and cups that stack up.

these lovely eggs get played with by 4 yr old and 1 yr old in our house. i'm pretty sure you can get them in woollies

Have also got a tunnel from Ikea, cheap, easy to store and my dd loves it.

Teaset from ELC , £5, dd is 29 months now and still plays with it nearly every day.

I have a few Little Tikes things, nearly all second hand. I got them from agencies/local paper and I've been really pleased with them. I got the cube with a slide last year, when dd was about 18 months and she played with it all summer.