Yellow Card

[Mrs Pingu]

If You're a Cyclist, Throw This Magnet at the Next Car Who Endangers Your Life

or just give a moton a free fridge magnet.

[Kim]

Expensive, implausible (I tend to be too busy swearing and making evasive manoeuvres for that sort of thing) and unlikely to end well.

Plus there's the pokemon effect.

[alexb]

Alternatively:

[andygates]

I favour crackback, but let's face it, stickering cars in media res is just the Ghandi remix of Spike Bike fantasies. 

[Pingu]

"The next car who endagers your life" 

[andygates]

"The next car that is driven in such a manner as to endanger your life" doesn't scan so good, and you can't throw it at the driver, because fridge magnets make lousy shuriken.

[Kim]

fridge magnets make lousy shuriken.

Rule 33?

[GrahamG]

Hmmm, how to make friends and influence people, eh?!  I've seen a few cyclists out there that ride like complete twats and then have a go at the nearest driver when it bites them in the arse - those are the only people who would consider doing something so utterly pointless and it'd wind anyone up on the receiving end, myself included.

[Steve Kish]

I've seen a few cyclists out there that ride like complete twats and then have a go at the nearest driver when it bites them in the arse

.... and it's because of these twunts that a lot of experienced and quite considerate cyclists are tarred with the same brush by a lot of motorists.

I've been tempted to wear a vest saying 'I don't jump red lights, use hand signals, ride quite sensibly, accept that there are other road users apart from me and don't ride on the pavement'.  However, the print would be too small.

[Cudzoziemiec]

It's wordy and comes over holier than thou. You might as well stop the car by force and then, depending on disposition, either beat the driver to a pulp or lie prone with a t-shirt "I'm a self-righteous twat, please drive over me."

[Nightfly]

Totally absurd and bonkers.

Many cars now have plastic/fibre glass panels to save weight so how would this supposed magnetic card stick to a car?

[andygates]

Many cars now have plastic/fibre glass panels to save weight so how would this supposed magnetic card stick to a car?

See, that's the voice of reason. 

Not only is it sanctimonious wank (wanktimonious?) but it just wouldn't work!

[alexb]

I've seen a few cyclists out there that ride like complete twats and then have a go at the nearest driver when it bites them in the arse

.... and it's because of these twunts that a lot of experienced and quite considerate cyclists are tarred with the same brush by a lot of motorists.

I've been tempted to wear a vest saying 'I don't jump red lights, use hand signals, ride quite sensibly, accept that there are other road users apart from me and don't ride on the pavement'.  However, the print would be too small.

You forgot to add "I have 3rd party insurance, a job and am zero rated for "road tax*""

* Yes I know, but the ignorant masses don't

[Steve Kish]

Amend to read 'looking for work'.