try $nick e.g.
Code:
%rr2 = $rand(1, $nick(0))
if (%rr = 1/2/3) .timer 1 3 msg $chan <...> $nick(%rr2) <...>


There is a race condition here - if someone leaves the channel within the 3 seconds the timer is set for, the above modifications will either give the wrong name, or an error.

One way around it is to set the nick as soon as the alias is triggered.
Code:
 
var %targetnick = $nick($rand(1, $nick(0)))

and use %targetnick instead of $2

Cheers,
DK