Etymotic ER20 (or Hearo Hi-Fidelity plugs, which are the same thing), but it's a bit of a pain in the ass figuring out which size to get the first time (basically buy both the large and the "standard" (small) and try them and eat the cost). And I usually bring a pair or two of cheap foamies that will cut 32 dB, just in case it's absolutely brutal; though the foamies muddy the highs too much. The ER20s will only cut around 12-20 dB with less of an impact on clarity, though there is still an impact.
Also make sure you twist them when you pull them out, I fucked my eardrum on Saturday at a concert with an absent-minded pull-out, and I totally knew better. So no ringing or muddied sound post concert, but two days of ear popping and painful yawns). Oops.
See, I wasn't sure if I should go the ER20s or the ETY Plugs. The Etymotic website has an ETY Plug combo w/ both sizes for the same price as the ER20s which is quite tempting.
I don't go to concerts much, but my right ear hasn't been picking up bass all that great lately and higher frequencies are beginning to hurt. Thanks for convicing me to go with Etymotic though!