If I were to limit myself hmm...
with current kit:
SIgma 24mm f2.8 AF Super Wide II
M 50 f1.4
why these two... I only have three primes. The other is the DA35 and while it is freaking sharp, it's not as fast as the M 50 nor is it as wide as the Sigma 24....
dream kit:
FA31 Ltd or FA*24mm f2 (
if it is weathersealed)
DFA 100mm f2.8 Macro WR
reasons:
FA31 Ltd: on film and on APS-C, has one of the best color rendering and sharpness combined, also, wider than a 35. The F28 would've been great but it's only f2.8 max.
FA*24: it's wide, it's fast. that's it.
DFA 100: the FL is flexible enough for portraiture and 1:1 macro use. also, it's WR