i used to work at this argentine restaurant and the manager still hooks me up w/ argentine beef cuts... soo tastey... just salt/pepper to taste, the natural flavor is AMAZING, everyone should try some argentine beef.
as for chicken... i can't find any better marinade than a basic italian dressing. Oh and if you have time look up "beer butt chicken" i got this thingy for my bbq where u put the chicken standing up w/ a half drinken beer in its ass...then the heat foams the beer up as you cook it and lets it soak through the chicken. It comes out exceptionally juicy and surprisingly flavorfull