In this paper we study a new ideal $\mathcal{ WR}$. The main result is the following: an ideal is not weakly Ramsey if and only if it is above $\mathcal{ WR}$ in the Kat\v{ e}tov order. Weak Ramseyness was introduced by Laflamme in order to characterize winning strategies in a certain game. We apply result of Natkaniec and Szuca to conclude that $\mathcal{ WR}$ is critical for ideal convergence of sequences of quasi-continuous functions. We study further combinatorial properties of $\mathcal{ WR}$ and weak Ramseyness. Answering a question of Filip\'ow et al. we show that $\mathcal{ WR}$ is not $2$-Ramsey, but every ideal on $\omega$ isomorphic to $\mathcal{ WR}$ is Mon (every sequence of reals contains a monotone subsequence indexed by a $\mathcal{ I}$-positive set).
Categories: math.CO