honda k20a !!
Domestic: Keith Black Hemi, or the 765c.i. hemi-headed Ford nitrous motor we did at work a while back. It broke the damn dyno.
Euro: Old school all motor 911 engine.
Jap: Not very outlandish, but a really well built ITB'd BP Miata stroker engine with stout internals and a 10k rev limiter.