Nidoqueen

Nidoqueen is whatever you want it to be. Really, Nidoqueen is used to fill in gaps in a team, and to be played defensively. Nidoqueen is a great Pokemon with a nice typing, which makes it immune to Electric, 4x resistant to Poison, and 2x resistant to Fighting, Bug, and Rock. Sure, a few of its weaknesses are pretty common, but every Pokemon has weaknesses. Nidoqueen could work in OU, given its immunity to Thunder Wave and Toxic, and its all-around usefulness. You could mix and match the moves above to make it a useful Curse counter. Really, Nidoqueen can fill in almost any role you may need on a team. Nidoqueen's versatility is what makes it so useful and fun to use. Facing one can be annoying though, since it has a large movepool at its disposal and its standard set has excellent type coverage, and several other movesets are possible.