I'll have a go at anything that tries, provided the conditions and areas allow. Town centres / residential areas / schools or anything similar are race tracks for those who shouldn't be allowed to drive. Having had a mate wheelchair bound with barely any control over any of his body at 11 years old, I've seen the effects first hand.
On a motorway, country roads I know (night time especially!), sweeping links of roundabouts (A43!) then I will have a play. If people start weaving through traffic, I stop. If they start messing about, I stop. If it's all good fun and just seeing how things fair in petrol and rubber, I'm ok with that.
In answer to the question, the most fun has been Mini Cooper S GP Works, and Lambo Gallardo Spider and a 911. With varying results. All did end with a smile and a thumbs up.