You can use the following construct to draw the error bars yourself using any collection of geometric shapes available:
(* starting out with defining some points, errors etc. *)
pts = NestList[{#[[1]] + 1, #[[2]] + RandomReal[{0., 1.}]} &, {0,
RandomReal[]}, 19];
err = RandomReal[4, 20];
data = Table[{pts[[i, 1]], pts[[i, 2]], err[[i]]}, {i, 1, Length@pts}];
hw = 1; (* the width of the ticks *)
ErrorListPlot[data, ErrorBarFunction -> Function[{coords, errs}, {
(* the vertical line: *)
Line[{coords - {0, errs[[2, 1]]/2}, coords + {0, errs[[2, 1]]/2}}],
(* horizontal tick 1: *)
Line[{coords - {hw/2, -errs[[2, 1]]/2}, coords + {hw/2, errs[[2, 1]]/2}}],
(* horizontal tick 2: *)
Line[{coords - {hw/2, errs[[2, 1]]/2}, coords + {hw/2, -errs[[2, 1]]/2}}]
}]]
Example:
