Sonny, Catalyst of Change

Defender
This card gains a +0/+1 counter for each artifact attached to it or other creatures you control.
{w/u}{w/u}{w/u}{w/u}{w/u}{w/u},{t}, This creature can sacrifice any
number of +0/+1 counters you control to tap
that number of attacking creatures. Those
creatures don't untap during their owner's
next untap step.