Cenchrus brownii - before I forget again and have to hunt the web for the scientific name!
Its quite common along the beach forest and it was first recorded in Singapore in 1950. I browsed the www and realised that the plant is in some flickr sets in Singapore without the name (I commented on them).. so here's the name so that the next time someone gets poked by it, at least can curse it properly.
Here's a nice picture of it courtesy of Ria from wildsingapore
It belongs to the grass family and not the sedge family.
Cenchrus brownii -!
As you can see, I am pretty invigorated by the fieldtrip I had this morning...