The April Fools post on TF2.com was no joke, not only is the Sniper getting the next class update (as was revealed afterwards), but you'll be getting a jar of piss tossed in your face as well.
Jarate is going to be the Killtaunt for the Sniper.
As of yet it is unknown what item it will be associated with, but rest assured pressing G (the default key for taunting) will trigger an animation of our psudo-Australian friend pulling out a large container of whizz and letting it fly.
Expect it to have a range that would be unlimited were it not for the fact that Jars of Piss tend to be affected by Gravity.
An Arcing effect that is somewhat more than that of the Needleguns will probably be what you'll see come the Sniper Update.
Still think it's a joke? If you look at the TF2.com blog, you'll see that VALVe never said anything about it being such.
April Fools no more, get ready to start practicing your Jarate skills so that you can pull off some of those all too awesome (and infuriating) Tauntkills.
[Because there's to many clueless people on the steampowered forums I added this bit]
(TF2.com is the official TF2 Blog made by VALVe)
Jarate: http://tf2.com/post.php?id=2391
EDIT:
I doubt that the piss would kill anybody, it's the shards of the glass jar that'd probably be the thing to do you in.
EDIT OF SUPREME 1337N3SS:
http://www.teamfortress.com/sniper_vs_spy/
Tauntkill no more, JARATE IS THE FREAKING SMG REPLACEMENT!