The first one that comes to mind is Michael Thomas who scored for Arsenal against Liverpool in the last seconds of the league giving Arsenal the Championship.
Another one is Nicolas Anelka (Ars - 97-99) (Liv - 2002 loan)
Jermaine Pennant Nicolas Anelka
One of the players who played for both arsenal and Liverpool is Nikolas Anelka ( also played for chelsea , West Brom ) Another Player is Yossi Bennoyoun
Played For Arsenal and BarcelonaPetit OvermarsHenryGio Van bronkhorstHleb
Michael Owen has played for both liverpool and currently Manchester united
Only Nicholas Anelka that I can think of from recent times.
Several players have notably played for both Arsenal and Inter Milan, including Emmanuel Adebayor, who had a brief stint at Inter after his time with Arsenal. Other players include Gianluca Vialli, who played for Arsenal early in his career before achieving fame at Inter. Additionally, there's also the case of Lukas Podolski, who joined Inter Milan on loan after his tenure at Arsenal.
There've been a few: I'll start with Ray Kennedy and Michael Thomas, and then sit back...
Phil Neal, Peter Bearsley, Paul Ince and Ramon Calliste
Phil Neal, Peter Bearsley, Paul Ince and Ramon Calliste
Frank Stapleton Viv Anderson George Graham Brian Kidd
Ljungberg Hartson Wright Winterburn Suker Benayoun
Arsenal (last win 2005) lead 10-7 against Liverpool (last win 2006). Arsenal also have the edge in finals between the two, leading the series 2-1 with wins in 1950 and 1971, against Liverpool's triumph in 2001.