1 and 2 to update display and render flags
I use this all the time, I think a hangover from using nuke too much. With the current node selected, hit 1 to set its display flag to here, 2 to set its render flag. This is often much faster than trying to hit that tiny blue rectangle.

Hitting 1 repeatedly cycles between the selected node and the last created node, handy for doing a quick comparisons (analogous to nuke and setting 1 to a node, 2 to another, and tapping 1 2 1 2 to compare them)

In H16 these 1 and 2 hotkeys have been replaced with R and E.

With the current node selected, hit _ to set its display flag to here

Hitting _ repeatedly cycles between the selected node and the last created node, handy for doing a quick comparisons

raincole
R and E do toggle flags, but the way they work is completely different from what CGWiki describes. R activates a "flag toggle mode" and I have to click the node after.

tamte
also to toggle between 2 nodes, just select 2 nodes and hit R repeatedly, it will swap display flag between them
or T for render flag
flags that can be set on multiple nodes simultaneously like template E or bypass Q will toggle them on all selected nodes together

tamte

raincole
R and E do toggle flags, but the way they work is completely different from what CGWiki describes. R activates a "flag toggle mode" and I have to click the node after.

I believe by default they should work on selected nodes, if not just make sure Preferences/NetworkEditor/FlagHotkeysWorkOnSelectedNodes is checked

also to toggle between 2 nodes, just select 2 nodes and hit R repeatedly, it will swap display flag between them
or T for render flag
flags that can be set on multiple nodes simultaneously like template E or bypass Q will toggle them on all selected nodes together

<?xml version="1.0" encoding="UTF-8"?>
<mainMenu>
    <menuBar>
        <subMenu id="custom_network_tools">
            
            <modifyItem>
                <insertAfter>help_menu</insertAfter>
            </modifyItem>
            
            <label>Custom</label>
            
            <scriptItem id="toggle_node_flags">
                <label>Toggle Render/Display Flag</label>
                <scriptCode><![CDATA[
import hou

selected = hou.selectedNodes()

if len(selected) == 2:
    node_a, node_b = selected[0], selected[1]
    
    if node_a.isRenderFlagSet():
        node_b.setRenderFlag(True)
        try: node_b.setDisplayFlag(True)
        except: pass
    else:
        node_a.setRenderFlag(True)
        try: node_a.setDisplayFlag(True)
        except: pass

elif len(selected) == 1:
    current_node = selected[0]
    last_path = hou.getenv("LAST_FLAGGED_NODE", "")
    
    if current_node.isRenderFlagSet() and last_path:
        last_node = hou.node(last_path)
        if last_node:
            last_node.setRenderFlag(True)
            try: last_node.setDisplayFlag(True)
            except: pass
    else:
        parent = current_node.parent()
        flagged_nodes = [n for n in parent.children() if n.isRenderFlagSet()]
        if flagged_nodes:
            hou.putenv("LAST_FLAGGED_NODE", flagged_nodes[0].path())
            
        current_node.setRenderFlag(True)
        try: current_node.setDisplayFlag(True)
        except: pass
]]></scriptCode>
            </scriptItem>
            
        </subMenu>
    </menuBar>
</mainMenu>

AnimGraphLabGames
Not sure what's up but it doesn't work in H21 for me. It deselects right after first "R" is pressed press. "T" shortcut jumps between 2 selected nodes though.