Which sets would you recomend buying?

One of these days i may have an occasion to go to a store that has a lot of lego, including Sonic sets (well, i hope so, last time i went there they had a lot) and i'd like to expand my little collection, which of the sets maybe you like the most and would recomend buying?

Forgot to mention i have the biolizard and shadow lab escape.

Thank you!